Mars is the fourth planet from the Sun and the one backyard astronomers chase hardest, because for a few months around each opposition it swells into a genuine, detail-rich disc through the eyepiece. I have been imaging the planets since 2008, and from my remote rig at Deepsky Chile — an Alluna 12.5″ Ritchey–Chrétien on a Paramount MX+ — the red planet remains the single most rewarding and most frustrating target in the sky. This guide explains what Mars actually is, why it glows orange-red, what you can see on its surface, how its opposition cycle works, and exactly how to observe and photograph it yourself.

What is Mars and why is it called the red planet?

Mars is a small, rocky terrestrial planet a little over half the diameter of Earth. It orbits the Sun every 687 Earth days at an average distance of about 228 million kilometres, roughly 1.5 times Earth’s distance. Despite its forbidding cold — average surface temperatures sit near −60 °C — it is the most Earth-like planet we know, with seasons, polar ice, wind, weather, and a day (a “sol”) of 24 hours and 37 minutes.

The famous colour comes from chemistry, not fire. The Martian regolith is loaded with iron, and over billions of years that iron oxidised — it literally rusted. Fine iron-oxide dust coats the surface and is lifted into the thin atmosphere by wind, giving the whole globe its butterscotch-to-ochre tint. So when ancient skywatchers named it after their gods of war for its blood-red glow, they were unknowingly describing planetary-scale rust.

How big is Mars compared with Earth?

Mars has a diameter of about 6,779 km against Earth’s 12,742 km, so it is roughly 53% as wide and has only about 11% of Earth’s mass. Surface gravity is about 38% of ours — a 100 kg person would weigh the equivalent of 38 kg there. That low gravity, combined with a thin carbon-dioxide atmosphere less than 1% the pressure of Earth’s, helps explain why Martian mountains and canyons grew to sizes that dwarf anything on our planet.

What are the main surface features on Mars?

Mars is a planet of superlatives. It hosts the largest volcano and the largest canyon system in the Solar System, plus bright polar caps that visibly wax and wane with the seasons. Even modest telescopes reveal some of these features when the planet is close.

Olympus Mons — the largest volcano in the Solar System

Olympus Mons is a shield volcano standing about 21.3 km high — roughly two and a half times the height of Mount Everest above sea level — and spreading some 600 km across its base, about the size of France. It grew so enormous because Mars has no shifting tectonic plates; a single hotspot kept erupting in the same place for hundreds of millions of years, piling lava ever higher instead of stringing out a chain of smaller volcanoes the way Earth does with Hawaii.

Valles Marineris — the Grand Canyon of Mars

Valles Marineris is a vast system of canyons stretching more than 4,000 km along the Martian equator, up to 200 km wide and as much as 7 km deep. If transplanted to Earth it would reach from New York to Los Angeles. It is not a river-carved canyon like Arizona’s but a tectonic rift — a colossal crack in the crust — later widened by landslides and erosion. You can read more in NASA’s overview of Valles Marineris.

The polar ice caps

Both Martian poles carry bright caps made of water ice with a seasonal overlay of frozen carbon dioxide (dry ice). They are the easiest surface feature to spot from your backyard: as Martian seasons turn, the cap facing us shrinks in local summer and regrows in winter, a change you can actually track over weeks of observing. For me, catching the brilliant white south polar cap during a favourable opposition is always the first “wow” moment of a Mars apparition.

How many moons does Mars have?

Mars has two tiny moons, Phobos and Deimos, discovered in 1877 by Asaph Hall. Both are small, dark, potato-shaped bodies, most likely captured asteroids or debris from an ancient impact. They are nothing like our own large, round Moon — and they are genuinely difficult targets for amateurs because they hide in the planet’s glare.

Phobos, the larger and inner moon, is only about 22 km across and whips around Mars in just 7.7 hours — faster than Mars rotates — so from the surface it would rise in the west and set in the east twice a day. It orbits so low that it is slowly spiralling inward and will eventually break apart or crash into Mars in tens of millions of years. Deimos is smaller still at about 12.6 km and orbits farther out every 30 hours. NASA keeps a concise reference on the moons of Mars. If you enjoy exotic satellites, you may also like our wider guide to planetary moons.

What is Mars opposition and when is the next one?

Mars opposition is the moment when Earth passes directly between Mars and the Sun, so the red planet sits opposite the Sun in our sky — rising at sunset, riding high at midnight, and setting at dawn. Because we are also at our closest, Mars appears biggest and brightest. This is the window every Mars observer waits for.

Oppositions repeat roughly every 26 months, because Earth has to “lap” the slower-orbiting Mars. The last one was on 16 January 2025, which means Mars is not at opposition in 2026 — through 2026 it is on the far side of its cycle, small and distant. The next opposition falls around 19 February 2027. Mark it: that is when planning, equipment tuning, and clear-sky luck should all come together.

Why are some oppositions better than others?

Mars has a noticeably elliptical orbit, so not all oppositions are equal. When opposition happens near Martian perihelion (its closest point to the Sun), Mars can swell to about 25 arcseconds across, as it did spectacularly in 2003 and 2018. The 2025 and 2027 oppositions are “aphelic” — Mars stays farther away and peaks nearer 14 arcseconds. Smaller, yes, but for northern observers these apparitions place Mars high overhead, which steadies the view and often beats a big-but-low disc boiling in the murk near the horizon.

How do you see Mars with the naked eye?

Learning how to see Mars without any equipment is the easiest first step: it is one of the brightest objects in the night sky near opposition and shines with a steady, distinctly orange-pink light. Unlike a star, it does not twinkle much, and its colour gives it away among the white and blue-white stars around it.

To find it, check where the planet currently sits along the ecliptic — a planetarium app or our Solar System hub will show you which constellation hosts it tonight. During 2026, with Mars far from opposition, expect a modest orange “star” rather than a beacon; save your high expectations for late 2026 into early 2027 as it brightens toward the February 2027 event. Mars observing rewards patience: even naked-eye, tracking how it drifts month to month against the stars is a genuine pleasure.

How do you observe Mars through a telescope?

Mars observing through a telescope is the real prize, but it is demanding because the disc is small. Here is the practical approach I use after years of planetary work.

Aperture, magnification and a Barlow

You can glimpse the polar cap and the largest dark markings in a 4-inch (100 mm) scope, but 6 to 10 inches of aperture transforms the view. Mars rewards high magnification — aim for around 200x to 350x when the air is steady. A good 2x or 2.5x Barlow lens paired with a quality eyepiece is the cleanest way to reach those powers without buying a drawer full of short-focal-length eyepieces. Push too hard, though, and you simply magnify a blurry, boiling blob.

Seeing, timing and patience

Atmospheric “seeing” matters more than aperture for Mars. Observe when the planet is high in the sky, let your scope cool to ambient temperature for 30 to 60 minutes, and wait at the eyepiece — detail snaps into focus during brief moments of calm air. A colour filter helps too: an orange or red filter boosts contrast on dark surface markings, while a blue filter highlights clouds, hazes and the polar caps. Want to confirm what fits in your view? Our telescope field-of-view calculator takes the guesswork out of eyepiece and Barlow combinations.

Watch for dust storms

One uniquely Martian hazard: global dust storms. Every few Martian years, regional storms can balloon into planet-encircling events that erase surface detail for weeks — the great 2018 storm did exactly that during a prime opposition. If your familiar dark markings suddenly fade to a bland orange disc, you may be watching a dust storm unfold in real time. It is frustrating and fascinating in equal measure.

How do you photograph Mars?

Imaging Mars relies on a technique called “lucky imaging.” Instead of one long exposure, you record a high-frame-rate video — thousands of frames over a couple of minutes — then use software to keep only the sharpest frames where the atmosphere briefly steadied, and stack them into one clean image.

My workflow from Deepsky Chile

From my Alluna 12.5″ RC on the Paramount MX+, I run a fast planetary camera at high frame rates through a Barlow to reach an effective focal ratio around f/15 to f/20. I capture short videos in AutoStakkert, stack the best 5–10% of frames, then sharpen with wavelets in RegiStax or AstroSurface, finishing colour balance and detail in PixInsight. The dark Chilean skies and high altitude give steadier seeing than most backyards, but the core method is identical at any aperture.

Beat the rotation and the clock

Because Mars rotates in about 24 hours 37 minutes, surface features visibly move during a long capture. Keep each colour-camera run under roughly three to four minutes to avoid smearing detail, or use de-rotation software to combine longer sequences. To plan exposure and signal targets across different setups, I lean on our astrophotography calculator. If planetary imaging hooks you, the same lucky-imaging discipline applies to Jupiter and Saturn — Mars is simply the most unforgiving of the three.

What missions and rovers have explored Mars?

Mars is the most explored planet beyond Earth. Decades of orbiters, landers and rovers have mapped it in extraordinary detail and are actively searching for signs that it was once habitable.

NASA’s Curiosity rover has been climbing Mount Sharp inside Gale Crater since 2012, while the Perseverance rover, which landed in Jezero Crater in 2021, is collecting rock cores for an eventual sample-return mission and flew the first powered aircraft on another world, the Ingenuity helicopter. Orbiters from NASA, ESA, India, the UAE and China continue to study the atmosphere, ice and geology from above. For an authoritative, regularly updated overview, NASA’s Mars exploration program is the best starting point. To put Mars in context with its neighbours, browse our planets overview, the rocky inner world Mercury, and the small bodies of the asteroid belt just beyond Mars’s orbit.

Frequently asked questions

Why is Mars red?

Mars is red because its surface soil and dust are rich in iron oxide — the same compound as common rust. Iron in the Martian crust oxidised over billions of years, and fine reddish dust now coats the planet and fills its thin atmosphere, giving Mars its characteristic orange-red colour.

When is the next Mars opposition?

The next Mars opposition is around 19 February 2027. The most recent one was on 16 January 2025, so Mars is not at opposition during 2026 and appears relatively small and faint that year. Oppositions recur roughly every 26 months as Earth catches up to and passes Mars.

Can you see Mars without a telescope?

Yes. Mars is easily visible to the naked eye and looks like a bright, non-twinkling orange star. It is most striking around opposition; far from opposition, as in much of 2026, it appears as a modest orange point. A simple planetarium app will show you exactly where to look on any given night.

What can you actually see on Mars through a telescope?

With a 6-inch or larger telescope at 200x or more during good seeing, you can see the bright white polar cap, dark surface markings such as Syrtis Major, and occasionally clouds or dust storms. The disc is small, so high magnification, steady air and patience at the eyepiece are essential.

How do astrophotographers get sharp images of Mars?

They use lucky imaging: recording a high-frame-rate video of thousands of frames, then stacking only the sharpest ones in software like AutoStakkert and sharpening with wavelets. A Barlow lens brings the effective focal ratio to about f/15–f/20, and short capture runs prevent Mars’s rotation from smearing surface detail.

Mercury is the smallest planet in our solar system and the closest to the Sun, and it is also one of the most rewarding naked-eye targets you can chase from a backyard or a dark site. I have been photographing the night sky since 2008, and I still remember the thrill of catching this tiny, fast-moving world hanging low in the twilight for the first time. Unlike the bright, patient giants such as Jupiter and Saturn, Mercury hides in the glare of the Sun and only shows itself for a short window every few weeks. That elusiveness is exactly what makes it such a satisfying observing challenge.

In this guide I will walk through the essential Mercury planet facts, explain its extreme environment and battered surface, cover the BepiColombo mission that arrives in 2026, and then give you concrete, field-tested advice on how to see Mercury and photograph it safely. There is one rule I will repeat more than once because it genuinely matters: never sweep your optics toward the Sun.

What is Mercury and why is it the smallest planet?

Mercury is the innermost planet of the solar system, orbiting at an average distance of about 58 million kilometres from the Sun. It is the smallest planet by a wide margin, with a diameter of roughly 4,879 kilometres — only about 38% the size of Earth and not much larger than our own Moon. Since Pluto was reclassified as a dwarf planet in 2006, Mercury has held the title of the smallest of the eight major planets.

Despite its small size, Mercury is dense. It has an enormous iron core that makes up a huge fraction of its volume, which is why it is the second-densest planet after Earth. That oversized core also gives Mercury a weak but genuine global magnetic field, something none of the other rocky inner planets except Earth possess. For more on how Mercury fits among its neighbours, see our overview of the planets of the solar system.

How fast does Mercury orbit?

Mercury is the fastest planet, completing one orbit of the Sun in just 88 Earth days — which is why the Romans named it after the swift messenger god. Its speed in our sky is exactly what makes it so hard to catch: it darts out from the Sun’s glare and slips back in within a matter of weeks. A Mercury “year” is shorter than three Earth months.

Why does Mercury have such extreme temperatures?

Mercury endures the most extreme temperature swings of any planet in the solar system. Because it sits so close to the Sun and has almost no atmosphere to trap or redistribute heat, the dayside can reach around 430 °C (about 800 °F) while the nightside plunges to roughly −180 °C (about −290 °F). That is a swing of more than 600 degrees between day and night.

You might assume the closest planet to the Sun would also be the hottest planet overall, but it is not — Venus is hotter, because its thick carbon-dioxide atmosphere traps heat in a runaway greenhouse effect. Mercury has no such blanket. Its tenuous “exosphere” is so thin it barely qualifies as an atmosphere at all, composed of atoms blasted off the surface by the solar wind and micrometeorite impacts.

Is there ice on the smallest planet?

Remarkably, yes. Despite the searing daytime heat, radar observations and NASA’s MESSENGER spacecraft confirmed that permanently shadowed craters at Mercury’s poles hold deposits of water ice. The planet’s axis is almost perfectly upright — it has virtually no axial tilt — so the floors of polar craters never see sunlight and stay cold enough to preserve ice for billions of years. It is one of the great contradictions of the solar system: frozen water surviving on the planet nearest the Sun.

What does Mercury’s surface look like?

Mercury’s surface looks strikingly like our Moon: grey, airless, and saturated with impact craters that have accumulated over billions of years. With no thick atmosphere and no active plate tectonics to erase them, those scars endure. The most dramatic feature is the Caloris Basin, an enormous impact crater roughly 1,550 kilometres across — one of the largest impact structures in the entire solar system. The collision that formed it was so violent that it created jumbled, hilly terrain on the exact opposite side of the planet, the so-called “weird terrain.”

Mercury also has unique wrinkle-ridge features called “lobate scarps,” cliffs hundreds of kilometres long that formed as the planet’s iron core cooled and the whole world shrank slightly, buckling its crust. Mercury is, in effect, a planet that has been gently contracting over its lifetime. To explore how all these worlds compare, browse our hub on the solar system.

Does Mercury have any moons?

No. Mercury has no moons and no rings. It shares this trait only with Venus among the planets. Its proximity to the Sun makes it very difficult for a planet this small to capture and hold onto a satellite — the Sun’s gravity would tend to strip any moon away. So when you observe Mercury, you are looking at a lone, unaccompanied world.

What is a Mercury transit and when is the next one?

A Mercury transit happens when Mercury passes directly between Earth and the Sun, appearing as a tiny black dot crawling across the solar disk. These events are rare because Mercury’s orbit is tilted relative to Earth’s, so the alignment only works a handful of times per century. The last transits occurred in 2016 and 2019, and the next one is not until 13 November 2032 — so there is no Mercury transit in 2026. Transits only ever happen in May or November.

If you do plan to watch a future transit, the same safety rule applies as for any solar observing: you must use a certified, full-aperture solar filter on the front of your telescope. Mercury’s silhouette is so small that you need magnification to see it, and that means pointing at the Sun — which is only safe with proper, purpose-built solar filtration.

What is the BepiColombo mission to Mercury?

BepiColombo is a joint mission by the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA), launched in 2018 to study Mercury in unprecedented detail. It is only the third spacecraft ever sent to Mercury, following NASA’s Mariner 10 in the 1970s and the MESSENGER orbiter, which mapped the planet between 2011 and 2015.

BepiColombo carries two orbiters: ESA’s Mercury Planetary Orbiter, which studies the surface and interior, and JAXA’s Mio, which investigates the magnetic field and exosphere. After a long cruise involving multiple gravity-assist flybys of Earth, Venus, and Mercury itself, the spacecraft is on final approach. Following a thruster issue that pushed back the timeline, BepiColombo is set to be captured into Mercury orbit in November 2026, with the two orbiters separating and full science operations beginning in early 2027. You can follow the mission’s progress on the official ESA BepiColombo page.

How do you see Mercury with the naked eye?

The single most important concept for finding Mercury is greatest elongation — the point in Mercury’s orbit when it appears farthest from the Sun in our sky. Because Mercury orbits inside Earth’s orbit, from our viewpoint it never strays far from the Sun. At greatest elongation it reaches its maximum apparent separation (roughly 18 to 28 degrees depending on the geometry), and that is your window to spot it in a darker sky before the Sun is too high or too low.

There are two flavours. At greatest eastern elongation, Mercury appears in the evening sky, low in the west just after sunset. At greatest western elongation, it appears in the morning sky, low in the east just before sunrise. Each apparition lasts roughly two weeks around the elongation date.

When can I see Mercury in 2026?

Here are the 2026 greatest elongations to circle on your calendar:

• Evening (look west after sunset): 19 February, 15 June, and 12 October 2026.
• Morning (look east before sunrise): 3 April, 2 August, and 21 November 2026.

Not every elongation is equally good. The angle the ecliptic makes with the horizon matters enormously. From the Northern Hemisphere, spring evening apparitions and autumn morning apparitions tend to be best because Mercury climbs higher above the horizon haze. From the Southern Hemisphere the seasons flip. The June and October evening windows are worth prioritising this year.

What is the best technique for spotting it?

My field-tested routine is simple. About 30 to 45 minutes after sunset (or before sunrise for a morning apparition), find an observing spot with a flat, unobstructed horizon — the ocean, a plain, or a high ridge. Start with binoculars to locate the planet as a steady, pinkish-white “star” low down, then switch to naked-eye viewing once you know where to look. A planetarium app or our telescope field-of-view calculator can help you frame the right patch of sky in advance.

How do you photograph Mercury safely?

Photographing Mercury is a genuine challenge, and safety has to come first. Never sweep your telescope, binoculars, or camera lens toward the Sun while searching for the planet, especially during morning apparitions when the Sun is rising or evening apparitions while it is still up. Even a brief, accidental glimpse of the Sun through magnifying optics can cause permanent eye damage and instantly fry a camera sensor. Wait until the Sun is fully below the horizon before you point anything at the sky.

What gear and settings work best?

Mercury is small — its disk spans only about 5 to 13 arcseconds — so high-resolution planetary imaging requires a long focal length and a fast planetary camera shooting video that you later stack. From my remote rig at Deepsky Chile, where the air is exceptionally steady, I have had my best results capturing thousands of frames and keeping only the sharpest few percent. The same lucky-imaging approach works for any of the rocky inner worlds; the techniques transfer neatly to imaging Mars when it is well placed.

A few practical pointers from years of chasing this planet:

• Fight the low altitude. Mercury is always near the horizon, where atmospheric turbulence (poor “seeing”) blurs detail. Image when it is at its highest point during the apparition and when the air is calm.
• Watch the phases. Like Venus and the Moon, Mercury shows phases — crescent, half, and gibbous — as its position relative to Earth and the Sun changes. A telescope at high magnification reveals this clearly, and the changing phase is one of the most satisfying things to capture.
• Consider careful daytime imaging only with expertise. Experienced imagers sometimes shoot Mercury in daylight when it is higher in the sky, but this is genuinely dangerous because the Sun is up. I do not recommend it unless you have a permanent, precisely aligned setup with hard limits that physically prevent the optics from ever crossing the Sun.
• Use a red or orange filter. A coloured filter can cut through some of the low-altitude haze and improve contrast on the disk.

How do I know where the Sun is?

Always confirm the Sun’s position before you begin. For evening sessions, do not uncap your telescope until the Sun has clearly set below your local horizon; for morning sessions, pack up and cap your optics well before sunrise. Treat the Sun as a hard boundary you never cross. This discipline is the difference between a long, healthy career under the stars and a single careless mistake. For authoritative reference material on the planet itself, NASA’s Mercury exploration page and Britannica’s Mercury entry are excellent, accurate starting points.

Why is Mercury worth the effort?

Plenty of casual stargazers go their whole lives without knowingly seeing Mercury, even though it is bright enough to be obvious once you know when and where to look. That is precisely why it feels like such an accomplishment. Catching the smallest planet hanging in the deepening twilight, knowing it is roasting at 430 degrees on one side and freezing on the other, with BepiColombo closing in for arrival in 2026, connects you to the dynamic, living machinery of the solar system in a way few other targets do.

My advice: pick one of the 2026 elongations, scout a clear-horizon site in advance, and commit to a week of attempts. Weather and seeing will not cooperate every night, but persistence pays off. Once you have spotted Mercury once, you will find it far easier the next time — your eye learns the rhythm of the twilight, and the messenger planet stops being a mystery.

Frequently asked questions

Is Mercury the smallest planet in the solar system?

Yes. Since Pluto was reclassified as a dwarf planet in 2006, Mercury has been the smallest of the eight major planets, with a diameter of about 4,879 kilometres — roughly 38% the size of Earth and only a little larger than Earth’s Moon. It is also the closest planet to the Sun.

How can I see Mercury with the naked eye?

Look low in the west about 30 to 45 minutes after sunset during an evening (eastern) elongation, or low in the east before sunrise during a morning (western) elongation. Choose a spot with a flat, unobstructed horizon, and use binoculars to locate it first as a steady pinkish-white point of light.

When is Mercury at greatest elongation in 2026?

In 2026, Mercury reaches greatest elongation on 19 February, 3 April, 15 June, 2 August, 12 October, and 21 November. The February, June, and October dates favour evening viewing in the west; the April, August, and November dates favour morning viewing in the east.

Why does Mercury have no moons?

Mercury has no moons because it is small and sits very close to the Sun. The Sun’s strong gravity would tend to pull away or destabilise any satellite Mercury might capture, making it nearly impossible for the planet to hold onto a moon over long timescales. Venus is the only other planet without moons.

When does the BepiColombo spacecraft arrive at Mercury?

After a thruster issue delayed its timeline, the ESA and JAXA BepiColombo mission is scheduled to be captured into orbit around Mercury in November 2026. Its two orbiters will then separate and begin full science operations in early 2027, returning the most detailed data on Mercury since NASA’s MESSENGER mission.

The Moon is Earth’s only natural satellite, the brightest object in our night sky after the Sun, and—in my two decades behind a telescope—the single best target for anyone learning astrophotography. I’m Hamza Touhami, an astrophotographer since 2008 who runs a remote imaging rig at Deepsky Chile (an Alluna 12.5″ Ritchey-Chrétien on a Paramount MX+), and the Moon is where I tell every beginner to start. It is bright, forgiving, endlessly detailed, and it rewards patience faster than any deep-sky object ever will.

This guide covers how the Moon formed, why its phases happen, the difference between the near and far sides, what maria and craters actually are, eclipses and supermoons, and—most usefully—a practical, field-tested workflow for observing and photographing the Moon in 2026. If you want to plan your framing, our telescope field of view calculator shows exactly how the Moon fits your camera and scope.

How did the Moon form?

The leading explanation is the giant-impact hypothesis: about 4.5 billion years ago, a Mars-sized protoplanet that scientists call Theia collided with the proto-Earth. The oblique impact blasted molten debris into orbit, and that material accreted just beyond Earth’s Roche limit to form the Moon.

This theory is favored because the Moon’s composition closely mirrors Earth’s mantle, yet it is depleted in volatile elements and iron—exactly what you’d expect from material that was vaporized and re-condensed in a high-energy collision. Apollo sample isotopes match Earth so tightly that any competing model has to explain that similarity.

Why this matters for what we see

The impact origin explains why the Moon has a small iron core and a relatively low density. It also set up the large, dark plains we see today, because the early Moon stayed molten long enough for heavy material to differentiate and for later lava flows to fill enormous impact basins. That history is written across the surface every clear night.

Why does the Moon have phases?

Moon phases happen because we see different fractions of the Moon’s sunlit half as it orbits Earth—they are not caused by Earth’s shadow. Half the Moon is always lit by the Sun; what changes is the angle between the Sun, Earth, and Moon, which controls how much of that lit half faces us.

One common confusion: people assume the dark part of the Moon is in Earth’s shadow. It isn’t. Earth’s shadow only touches the Moon during a lunar eclipse. The rest of the time, the unlit portion is simply the part of the Moon’s own night side turned toward us.

The eight phases in order

• New Moon — the lit side faces away; the Moon is essentially invisible.
• Waxing Crescent — a thin sliver grows in the evening sky.
• First Quarter — half-lit; rises around midday, sets around midnight.
• Waxing Gibbous — more than half, still growing.
• Full Moon — fully lit; rises at sunset.
• Waning Gibbous — shrinking from full.
• Last Quarter — the other half lit; rises near midnight.
• Waning Crescent — a thin sliver before dawn.

The full cycle—new Moon to new Moon—takes about 29.5 days. This is the synodic month, and it’s slightly longer than the 27.3-day orbital period because Earth is also moving around the Sun, so the Moon has to travel a little farther to line up the same way again.

What is the difference between the near side and far side?

The near side is the hemisphere that always faces Earth; the far side is the one we never see directly from the ground. This happens because the Moon is tidally locked—its rotation period exactly equals its orbital period, so the same face is permanently turned toward us.

The two hemispheres look strikingly different. The near side is dominated by the large dark maria, while the far side is rugged, heavily cratered, and almost devoid of those smooth plains. The far side’s crust is thicker, which likely prevented as much lava from flooding its basins. It is not the “dark side”—both hemispheres receive sunlight equally over a lunar month.

Libration: seeing a little extra

Although the Moon is tidally locked, a wobble called libration lets us glimpse about 59% of the surface over time. The Moon’s slightly elliptical orbit and tilted axis mean it nods and rocks gently as seen from Earth. For imagers, libration is worth tracking because it briefly tips features near the limb into better view—Mare Orientale is the classic example.

What are maria and craters?

Maria (Latin for “seas”) are the large, dark, smooth plains of ancient solidified basaltic lava; craters are the round impact scars left by asteroids and comets over billions of years. Early astronomers mistook the maria for actual oceans, and the name stuck.

The maria formed when massive impacts punched through the crust and dark lava welled up to fill the basins roughly 3 to 3.5 billion years ago. The brighter, rougher regions between them are the older lunar highlands. Because the Moon has no atmosphere or active weather, its craters and rays are preserved with astonishing sharpness—which is exactly why it photographs so well.

Features worth hunting

• Copernicus — a young, terraced crater with a bright ray system.
• Tycho — in the southern highlands, with rays stretching across the disc at full Moon.
• Mare Tranquillitatis — the Sea of Tranquility, near the Apollo 11 landing site.
• Apennine Mountains — a dramatic mountain arc bordering Mare Imbrium.
• Plato — a dark-floored crater that stands out beautifully near the terminator.

For more on how the Moon fits into the broader family of worlds, see our overview of the solar system and our guide to the planets. The Moon is also part of a wider story—explore the other moons orbiting the giant planets to appreciate just how unusual our large, single satellite really is.

What are eclipses and supermoons?

A lunar eclipse happens when Earth passes directly between the Sun and Moon, casting its shadow on the lunar surface; a supermoon is a full Moon that occurs near the Moon’s closest approach to Earth, making it appear slightly larger and brighter. Both are easy, rewarding targets.

During a total lunar eclipse the Moon doesn’t vanish—it turns a coppery red, the famous “Blood Moon,” because sunlight bent through Earth’s atmosphere still reaches it. In 2026 a total lunar eclipse falls on March 3, visible from the Americas, with a partial lunar eclipse on August 28. A total solar eclipse—which involves the Moon passing in front of the Sun—occurs on August 12, 2026.

2026 supermoons

2026 brings three supermoons—on January 3, November 24, and December 23. The December 23 full Moon is the closest of the year at about 356,740 km, the nearest full Moon since 2019. A supermoon looks roughly 7% wider and noticeably brighter than an average full Moon, though the difference is subtle to the naked eye. For eclipse and Sun-related events, our developing Sun guide and meteor shower calendar round out the observing year.

How do you photograph the Moon?

The best way to photograph the Moon is to shoot along the terminator—the line dividing lit and unlit areas—at first or last quarter, where low-angle sunlight casts long shadows and reveals maximum crater relief. The full Moon, despite being the brightest, is actually the worst for detail because the flat, head-on light washes out texture.

This is the single most important lesson I share with beginners. People wait for the full Moon and come away disappointed by a flat, featureless disc. Shoot two or three nights before or after full—or better, at quarter phase—and the same telescope suddenly delivers dramatic, three-dimensional terrain.

Single-shot versus lucky imaging

There are two core techniques, and the right one depends on your gear and goals.

• Single-shot (DSLR/mirrorless): Attach a camera to your telescope at prime focus, or use a long telephoto lens (300mm+). One well-exposed frame can produce a sharp full-disc image. This is the fastest route to a satisfying result.
• Lucky imaging (planetary camera): Record a short video of a few thousand frames with a high-speed camera, then use software like AutoStakkert! to keep only the sharpest frames and stack them. This beats atmospheric turbulence and yields the crisp, high-resolution close-ups you see from serious lunar imagers.

For full-disc work I lean on single-shot frames; for crater close-ups I always use lucky imaging. Even from my remote RC at Deepsky Chile, stacking sharp moments out of a video clip consistently outperforms any single exposure when seeing conditions wobble.

Gear and exposure settings

You don’t need a huge instrument. A small refractor or any telescope from 60mm aperture upward will show craters beautifully. Here’s the practical starting point I recommend:

• ISO: 100–200 (the Moon is bright; keep noise low).
• Shutter speed: roughly 1/125 to 1/250 second for a full Moon; lengthen toward a thin crescent.
• Aperture (lens shots): f/8 to f/11 for a sharp result.
• Focus: manual, magnified live view on a crater edge—never autofocus.
• Stability: a solid tripod or tracking mount, plus a remote shutter or 2-second timer to kill vibration.

Shoot in RAW so you can recover contrast and sharpen in post. A tracking mount helps a great deal at high magnification, but for full-disc shots a sturdy tripod is enough. To work out whether the Moon will fill your frame or float in it, plug your setup into the field of view calculator, and use our astrophotography calculator to check focal length, sampling, and exposure together.

Processing your lunar shots

Light processing transforms a good capture into a great one. For stacked images, run the output through wavelet sharpening (RegiStax or PixInsight’s MultiscaleMedianTransform) to pull out fine detail. For single shots, modest contrast, a touch of unsharp mask, and careful highlight control are usually all you need. Resist over-sharpening—harsh halos around craters are the telltale sign of a heavy hand.

When is the best time to observe the Moon?

The best time to observe the Moon is during the first or last quarter, when the terminator slices across the disc and shadow detail is at its richest. A waxing crescent in the evening is also gorgeous, often showing “earthshine”—the faint glow on the unlit side reflected from Earth.

Plan around the phase, not just the clearest night. Check the Moon’s altitude too: higher in the sky means you look through less turbulent atmosphere, so detail holds together better. A night of steady seeing at quarter phase beats a crystal-clear full-Moon night every time for detail work.

A simple first session

1. Pick a night near first quarter and set up before dark.
2. Find the Moon, then focus carefully at high magnification on a crater near the terminator.
3. For visual observing, start at low power and increase magnification until detail softens, then back off.
4. For imaging, capture both a full-disc frame and a short close-up video clip.
5. Note the date and libration so you can compare features over a full lunar month.

Quick Moon facts

• Average distance: about 384,400 km from Earth.
• Diameter: roughly 3,474 km—about a quarter of Earth’s.
• Synodic month: 29.5 days (new Moon to new Moon).
• Orbital period: 27.3 days relative to the stars.
• Surface gravity: about one-sixth of Earth’s.
• Atmosphere: essentially none—an ultra-thin exosphere.
• Surface visible from Earth: about 59% over time, thanks to libration.

For authoritative deep dives, NASA’s lunar science portal and the European Space Agency are excellent references. See NASA’s Moon overview and the ESA Moon exploration pages for ongoing mission data, and Britannica’s Moon entry for a thorough scientific summary.

Frequently asked questions

Why does the Moon look bigger near the horizon?

The Moon doesn’t actually change size near the horizon—this is the “Moon illusion,” a trick of human perception. When the Moon sits low next to trees, buildings, and the landscape, your brain judges it as larger by comparison. Measure it with a camera and it’s the same size as when it’s overhead.

Can I photograph the Moon without a telescope?

Yes. A DSLR or mirrorless camera with a 300mm or longer telephoto lens on a tripod captures a recognizable, crater-dotted Moon. Even modern smartphones with optical zoom can grab a respectable shot. A telescope simply lets you reach far higher magnification and resolve fine detail like crater terraces and rilles.

What causes a Blood Moon?

A Blood Moon is a total lunar eclipse, when Earth passes between the Sun and Moon and casts its shadow on the lunar surface. The Moon glows red rather than going black because sunlight is refracted through Earth’s atmosphere, which filters out blue light and bends the remaining red light onto the Moon. The next one for the Americas is March 3, 2026.

Why is the full Moon bad for astrophotography of detail?

At full Moon, sunlight hits the surface head-on, so shadows vanish and the terrain looks flat and washed out. Crater walls, mountain ranges, and rilles only show their relief when sunlight strikes them at a low angle—which happens along the terminator near the quarter phases. That’s why experienced lunar imagers avoid full Moon for close-up work.

How far away is the Moon and is it moving?

The Moon orbits at an average distance of about 384,400 km, but it’s slowly drifting away from Earth at roughly 3.8 centimeters per year due to tidal interaction. Over hundreds of millions of years this gradually lengthens Earth’s day, too—though on any human timescale the Moon’s distance and appearance are effectively constant.

Written by Hamza Touhami, astrophotographer since 2008, who operates a remote imaging rig (Alluna 12.5″ RC, Paramount MX+) at Deepsky Chile and has spent countless nights chasing the lunar terminator.

Comets are among the most dramatic objects you can see or photograph in the night sky — icy wanderers that grow glowing heads and sweeping tails as they fall toward the Sun. I have been photographing them since 2008, and few targets reward patience the way a bright comet does. This guide explains what a comet actually is, where comets come from, the difference between short- and long-period comets, the famous ones worth knowing in 2026, and a hands-on workflow for observing and photographing them yourself.

What is a comet?

A comet is a small icy body — often called a “dirty snowball” — that orbits the Sun on a long, stretched path. So what is a comet made of? At its core sits a nucleus of frozen water, carbon dioxide, ammonia and methane, mixed with dust and rocky grains. For most of its orbit the comet is dark, cold and invisible, often only a few kilometers across.

Everything changes as a comet approaches the Sun. Solar heat causes the frozen ices to sublimate — turning directly from solid to gas — which releases dust and forms the spectacular features we see from Earth. Without that heating, a comet is just a frozen lump drifting in the dark.

For context on how comets fit alongside the other worlds in our neighborhood, see our overview of the solar system and how it compares with the major planets.

What are the parts of a comet?

The parts of a comet are the nucleus, the coma, and the tails — the dust tail and the ion tail. Each becomes visible only when the comet is active near the Sun. Understanding these parts is the key to both observing and photographing comets well.

The nucleus

The nucleus is the solid heart of the comet: a porous mix of ice, dust and rock, typically between 1 and 50 kilometers wide. It is extremely dark, reflecting only a few percent of sunlight — darker than fresh asphalt. The nucleus is the source of all the gas and dust that creates the rest of the comet’s anatomy.

The coma

As ices vaporize, they form a vast, roughly spherical cloud of gas and dust around the nucleus called the coma. The coma can swell to hundreds of thousands of kilometers across — larger than many planets. When you look at a comet through a telescope, the fuzzy glowing head you see is the coma, not the tiny nucleus hidden inside it.

The dust tail and the ion tail

A bright comet usually shows two distinct tails. The dust tail is made of fine particles pushed gently away by sunlight (radiation pressure); it appears yellowish-white and often curves along the comet’s orbital path. The ion tail (or gas tail) forms when ultraviolet light strips electrons from gas molecules, and the solar wind blows these charged particles straight away from the Sun. The comet tail structure is one reason every tail always points away from the Sun — not behind the comet’s direction of travel, as many people assume. That means a comet can appear to travel tail-first as it heads back out into the solar system.

Where do comets come from?

Comets come from two cold reservoirs at the outer edges of the solar system: the Kuiper Belt and the Oort Cloud. Both are leftover material from the formation of the planets some 4.6 billion years ago, preserved in the deep freeze of deep space.

The Kuiper Belt

The Kuiper Belt is a doughnut-shaped region beyond Neptune, stretching roughly from 30 to 50 astronomical units (AU) from the Sun. It is home to icy bodies including Pluto and many trans-Neptunian objects. Gravitational nudges occasionally send a Kuiper Belt object inward, where it becomes a relatively short-period comet. NASA describes the belt as a vast disc of icy remnants from the solar system’s birth (NASA Science — Comets).

The Oort Cloud

The Oort Cloud is a vast spherical shell of icy bodies thought to surround the solar system at distances of up to 100,000 AU — nearly a quarter of the way to the nearest star. It is the source of long-period comets. A passing star or galactic tide can dislodge an object from the Oort Cloud, sending it on a journey of thousands or even millions of years toward the inner solar system. The Oort Cloud has never been directly observed; its existence is inferred from the orbits of the long-period comets that arrive from every direction in the sky.

What is the difference between short-period and long-period comets?

The difference is orbital period: short-period comets complete an orbit in under 200 years, while long-period comets take longer — sometimes millions of years. This single number tells you where a comet came from and how often you can hope to see it again.

Short-period comets

Short-period comets mostly originate in the Kuiper Belt and have relatively flat, predictable orbits aligned with the plane of the planets. Halley’s Comet, with its 76-year orbit, is the most famous example. Because they return on human timescales, short-period comets can be observed and modeled across multiple apparitions, which makes their behavior far easier to forecast.

Long-period comets

Long-period comets fall in from the Oort Cloud on enormous, often nearly parabolic orbits that can be tilted at any angle. Many are seen only once in recorded history. These are frequently the brightest and most spectacular comets — but also the least predictable, since a fresh, ice-rich nucleus can flare unexpectedly or, just as easily, fizzle and crumble as it nears the Sun.

What are the most famous comets?

The most famous comets include Halley, Hale-Bopp, NEOWISE and Tsuchinshan-ATLAS — each a milestone for skywatchers. Below is a quick reference for the headline comets of the modern era.

Halley — the comet that started it all

Halley’s Comet is the only naked-eye comet that can return within a single human lifetime. Edmond Halley predicted its return in 1758, proving comets orbit the Sun. It last graced our skies in 1986 and reached aphelion — its farthest point at 35 AU — on 9 December 2023, meaning it is now slowly falling back toward us. Its next perihelion is forecast for 28 July 2061, and that apparition should be far brighter than 1986 (Halley’s Comet — Wikipedia). Halley is also the parent of two annual meteor showers, the Eta Aquariids and the Orionids.

Hale-Bopp and NEOWISE

Hale-Bopp dominated the sky for a record-breaking 18 months in 1996–97 and is the benchmark “Great Comet” for a whole generation. NEOWISE, in July 2020, was the brightest comet visible from the Northern Hemisphere in decades and became a global phenomenon during the pandemic summer — the comet that pulled countless people into astrophotography.

Tsuchinshan-ATLAS — the standout of recent years

Comet C/2023 A3 (Tsuchinshan-ATLAS) made its closest approach to Earth on 13 October 2024 at about 0.47 AU and peaked near magnitude −4.9 around 9 October — the brightest comet seen from the Northern Hemisphere since Hale-Bopp in 1997, with a tail stretching roughly 21 degrees across the sky. I imaged it from the Southern Hemisphere as it emerged at dawn, and it is the finest comet I have photographed in my remote-rig era.

How do you observe comets with the naked eye and binoculars?

To observe a comet, find a dark site away from light pollution, check its position for your date, and start with binoculars before reaching for a telescope. Most comets are diffuse, low-contrast objects, so dark skies matter more than aperture.

• Use a finder app or ephemeris to know exactly where and when the comet rises — many are best at dawn or dusk, low to the horizon.
• Start with 10×50 binoculars. Their wide field shows the coma and tail far better than a high-power telescope, which over-magnifies and dims the view.
• Let your eyes dark-adapt for 20–30 minutes and use averted vision — looking slightly to the side — to catch faint tail structure.
• Time it right. A comet is usually best within a week or two of perihelion or its closest approach to Earth.

How do you photograph comets?

To photograph a comet, use a tracking mount, shoot many short exposures, and stack them aligned on the comet’s nucleus rather than the stars. How to photograph comets well comes down to matching your gear and exposure to how fast the comet is moving against the background stars. Here is the workflow I use on my remote rig at Deepsky Chile (an Alluna 12.5″ RC on a Paramount MX+), adapted for portable setups too.

Choosing your gear: wide-field versus telescope

For a big, bright comet with a long tail — like NEOWISE or Tsuchinshan-ATLAS — a DSLR or mirrorless camera with a 50–200mm lens on a small star tracker captures the whole tail and the landscape context. A telescope is the wrong tool here: its narrow field crops the tail. Reserve the telescope for fainter, more compact comets where you want detail in the coma and inner tail. Before a session I plan framing with our telescope field of view calculator to confirm the tail will fit the sensor.

Camera settings and exposure

Comets move noticeably against the stars, so individual exposures must be short enough to keep the nucleus sharp. Start near these values and adjust:

• Wide-field lens: ISO 1600–3200, aperture f/2.8–f/4, 8–30 second subs on a tracker.
• Telescope: 30–120 second subs depending on the comet’s apparent motion; faster comets demand shorter subs.
• Shoot RAW, take dark and flat calibration frames, and gather as many subs as the comet’s altitude allows.

To dial in exposure time for your sky brightness and optics, our astrophotography calculator takes the guesswork out of sub-exposure length.

Stacking on the comet nucleus

This is the step that separates a smeared snapshot from a clean comet image. Because the comet drifts relative to the stars, normal star-aligned stacking blurs the comet, while comet-aligned stacking blurs the stars. The professional approach is to stack twice: once aligned on the stars and once aligned on the comet nucleus, then blend the two so both render sharp. Software such as PixInsight, DeepSkyStacker and Siril all offer dedicated comet-stacking modes — tell the program to register on the nucleus, and it compensates for the comet’s motion frame by frame.

Practical field tips from experience

• Polar-align carefully even for short subs — field rotation ruins the corners over a long sequence.
• Capture early. Comets near the horizon set or rise fast; you often have a 30–45 minute window in dark sky.
• Don’t over-stretch. The faint ion tail lives in the shadows; lift it gently to avoid amplifying noise and gradients.
• Mind the Moon. Plan around a dark Moon phase — moonlight washes out the delicate tail more than it does stars.

Are comets dangerous, and what can we learn from them?

Comets are not an everyday danger, but they are scientifically priceless. Impacts are rare on human timescales, and astronomers track near-Earth objects — including comets and asteroids — to give years of warning. Far more valuable is what comets teach us: as nearly unchanged relics from the birth of the solar system, they carry pristine ices and organic molecules. The ESA Rosetta mission, which orbited comet 67P/Churyumov-Gerasimenko and landed the Philae probe in 2014, found that comets likely helped deliver the raw ingredients for water and organic chemistry to the early Earth (ESA — Rosetta mission).

Frequently asked questions

What exactly is a comet made of?

A comet is made of frozen ices — mainly water, carbon dioxide, ammonia and methane — mixed with dust and rocky grains, which is why it is nicknamed a “dirty snowball.” Its solid core, the nucleus, stays frozen until it nears the Sun, when heat vaporizes the ices to form the glowing coma and tails.

Why does a comet’s tail always point away from the Sun?

Because the tail is shaped by solar radiation pressure and the solar wind, both of which flow outward from the Sun. They push the comet’s dust and ionized gas directly away from the Sun regardless of which way the comet is moving. On its outbound journey, a comet therefore appears to travel tail-first.

When will Halley’s Comet be visible again?

Halley’s Comet will next reach perihelion on 28 July 2061. It passed its farthest point from the Sun in December 2023 and is now slowly returning inward. The 2061 apparition is expected to be considerably brighter than its faint 1986 showing because the comet will be on the same side of the Sun as Earth.

What is the best comet to have appeared recently?

Comet C/2023 A3 (Tsuchinshan-ATLAS) in October 2024 was the standout, peaking near magnitude −4.9 — the brightest comet visible from the Northern Hemisphere since Hale-Bopp in 1997, with a tail about 21 degrees long. Before that, NEOWISE in July 2020 was the brightest in decades.

How do I photograph a comet without star trailing?

Use a tracking mount and keep individual exposures short — roughly 8–30 seconds with a wide lens, or 30–120 seconds through a telescope depending on how fast the comet moves. Then stack your frames twice, once aligned on the stars and once on the comet nucleus, and blend the results so both stars and comet stay sharp.

Written by Hamza Touhami, astrophotographer since 2008, imaging from a remote rig (Alluna 12.5″ RC on a Paramount MX+) at Deepsky Chile.

Asteroids are the rocky, airless remnants left over from the formation of our solar system roughly 4.6 billion years ago, and most of them orbit the Sun in a vast doughnut-shaped region between Mars and Jupiter called the main asteroid belt. I have been photographing the night sky since 2008, and few targets feel as quietly thrilling as catching one of these ancient worlds drifting visibly against the fixed stars over a single night. In this guide I will walk you through what asteroids are, how the asteroid belt is structured, the major asteroid types, the standout objects like Ceres and Vesta, the near-Earth asteroids that grab headlines, the spacecraft sent to study them, and exactly how you can observe and photograph the brightest ones in 2026.

What is an asteroid?

An asteroid is a small, rocky or metallic body that orbits the Sun but is too small to be a planet and shows no cometary tail. They are the rubble that never coalesced into a full-sized world, frozen as a snapshot of the early solar system.

Unlike planets, asteroids are not massive enough for gravity to crush them into a sphere — only the very largest, like Ceres, manage that. The rest are lumpy, cratered, and often shaped like potatoes or peanuts. The total mass of all asteroids combined is less than that of Earth’s Moon, yet there are millions of them larger than a kilometre across.

The word “asteroid” means “star-like,” because in a telescope these bodies look like faint, untwinkling points of light rather than the disks you see when you observe the giant planet Jupiter or Saturn. What gives them away is motion: track one over an hour or two and it visibly shifts against the background stars.

What is the asteroid belt and where is it?

The asteroid belt is a ring of rocky bodies orbiting the Sun between the orbits of Mars and Jupiter, roughly 2.2 to 3.2 astronomical units from the Sun. It is the solar system’s main reservoir of asteroids.

If you have ever wondered what is the asteroid belt made of, the honest answer is mostly empty space. Despite Hollywood’s crowded debris fields, the belt’s objects are typically separated by hundreds of thousands of kilometres. The dozens of robotic spacecraft that have flown through it never came close to hitting anything.

Why didn’t the belt form a planet?

Jupiter is the culprit. The giant planet’s immense gravity stirred up the orbital speeds of the planetesimals in this zone, causing them to collide too violently to stick together. Instead of building a planet, they ground each other down. Jupiter’s gravitational resonances also carved gaps in the belt — the Kirkwood gaps — where almost no asteroids survive on stable orbits.

You can put the scale of these orbits in perspective using a telescope field-of-view calculator to see how the angular motion of belt asteroids compares with closer objects. To see how the belt fits into the bigger picture, the overview of our solar system places it neatly between the rocky inner planets and the gas giants.

What are the main types of asteroids?

Asteroids are sorted into three broad spectral classes — C, S, and M — based on their composition and how they reflect sunlight. Each tells a different story about where and how it formed.

• C-type (carbonaceous): The most common, making up roughly three-quarters of known asteroids. They are dark, carbon-rich, and primitive — little changed since the solar system formed. They dominate the outer belt.
• S-type (silicaceous): Stony bodies rich in silicate minerals and nickel-iron. Brighter than C-types and more common in the inner belt. Vesta and many near-Earth asteroids fall here or in related groups.
• M-type (metallic): Relatively rare and made largely of nickel-iron metal. These are thought to be the exposed cores of shattered protoplanets — the target asteroid Psyche is the best-known example.

This compositional split matters for the future too: M-type bodies are the focus of speculative asteroid-mining plans because a single metallic asteroid could hold more iron, nickel, and platinum-group metals than humanity has ever mined on Earth.

What are the largest asteroids?

The four largest asteroids — Ceres, Vesta, Pallas, and Hygiea — together account for about half of the entire belt’s mass. Ceres alone holds roughly a third.

Ceres: asteroid or dwarf planet?

Ceres is both. Discovered in 1801, it was first called a planet, then reclassified as an asteroid, and in 2006 it was promoted to dwarf-planet status alongside Pluto. It remains the only dwarf planet in the inner solar system. NASA’s Dawn spacecraft orbited Ceres from 2015 and revealed bright deposits of sodium carbonate in Occator Crater — salty residue from briny water that seeped up from below. If you find dwarf worlds fascinating, the guide to the solar system’s dwarf planets covers Ceres, Pluto, Eris, and the rest.

What are near-Earth asteroids?

Near-Earth asteroids (NEAs) are asteroids whose orbits bring them within about 1.3 astronomical units of the Sun, carrying them close to Earth’s orbital path. They are the population astronomers watch most closely because a small fraction could one day strike our planet.

As of 2026, surveys have catalogued more than 36,000 near-Earth asteroids, and the count climbs every week as automated telescopes sweep the sky. Most are harmless, but a subset called potentially hazardous asteroids — larger than about 140 metres and passing especially close — are tracked with extra care.

Should we worry about an impact?

Not in any near term. NASA’s Center for Near-Earth Object Studies has ruled out any known asteroid posing a significant impact risk for the next century. The far greater danger comes from objects we have not yet discovered, which is why funding for sky surveys keeps growing. For a deeper look at the risk and what would actually happen, see our companion piece on whether an asteroid could hit Earth.

It is worth distinguishing asteroids from their icy cousins. The frozen bodies that grow tails are covered in our article on comets and how to observe them, while the distant frozen worlds beyond Neptune are explored in our guide to trans-Neptunian objects.

Which spacecraft have visited asteroids?

Several missions have flown past, orbited, landed on, and even returned samples from asteroids, transforming them from points of light into geological worlds. Two stand out for what they taught us in recent years.

DART: the first planetary-defence test

In September 2022, NASA’s DART (Double Asteroid Redirection Test) deliberately slammed into Dimorphos, a small moonlet orbiting the asteroid Didymos, to test whether a kinetic impact could change an asteroid’s orbit. It worked — the collision shortened Dimorphos’s orbital period by about 32 minutes, far more than predicted. DART proved that humanity could, in principle, nudge a threatening asteroid off course given enough warning time. The European Space Agency’s Hera mission is now en route to survey the aftermath up close.

OSIRIS-REx and OSIRIS-APEX

NASA’s OSIRIS-REx grabbed a sample from the near-Earth asteroid Bennu and parachuted it back to Earth in September 2023. Analysis announced in 2025 found a rich brew of organic molecules in the sample, including 14 of the 20 amino acids used by terrestrial life and all four DNA and RNA nucleobases — powerful evidence that asteroids delivered life’s raw ingredients to the early Earth. The spacecraft, now renamed OSIRIS-APEX, is heading for a 2029 rendezvous with Apophis after that asteroid’s famously close pass by Earth on 13 April 2029. Japan’s Hayabusa2 achieved a similar sample return from asteroid Ryugu in 2020.

How can amateurs observe and photograph asteroids?

Yes — the brightest asteroids are well within reach of binoculars, small telescopes, and beginner astrophotography setups, and watching one move over a single night is one of the most rewarding things you can do at the eyepiece. Here is how I approach it.

Start with Vesta

Vesta is the brightest asteroid and the only one that can reach naked-eye visibility from a dark site. In 2026 it is exceptionally well placed: a rare double opposition puts it at magnitude 5.7 on 2 May 2026 in Libra, then again at magnitude 6.3 on 13 October 2026 in Pisces. At the May opposition you can sweep it up in any binoculars from suburban skies, and it stays visible for weeks around that date.

Confirm it by its motion

An asteroid looks identical to a faint star in a single glance, so the trick is to record its position and check again the next clear night. I print a finder chart from planetarium software, mark the predicted track, and sketch or photograph the field. Over 24 hours a belt asteroid shifts noticeably; over a week the movement is obvious. That little “aha” moment of seeing a dot has wandered never gets old, even after photographing the sky since 2008.

Imaging tips from my own rig

For photography you do not need anything exotic. A tracked DSLR with a 200 mm lens will capture Vesta and Ceres easily, and stacking a series of short exposures lets you build a time-lapse of the asteroid creeping across the frame. With my remote setup at Deepsky Chile — an Alluna 12.5-inch Ritchey-Chrétien on a Paramount MX+ — I can reach asteroids down to 16th or 17th magnitude, but that level of gear is overkill for the bright belt members. A few practical pointers:

• Keep exposures short. Thirty to sixty seconds avoids trailing the asteroid relative to the stars while you build signal.
• Shoot the same field on two nights. Blink the two frames and the moving dot jumps out instantly.
• Use accurate ephemerides. Free tools and apps give precise nightly positions; load the coordinates before you set up.
• Pick opposition. Asteroids are brightest and best placed when opposite the Sun in our sky, mirroring how Mars brightens dramatically at its own oppositions.

If you want to plan which asteroids clear your local horizon, cross-reference their positions with the broader guide to observing the planets, since the brighter asteroids share the same ecliptic band as the planets and often sit near them in the sky. For more on the major small bodies, the NASA asteroids overview is an excellent authoritative reference.

Frequently asked questions

What is the difference between an asteroid and a comet?

Asteroids are rocky or metallic bodies that formed in the warmer inner solar system and generally have no tail, while comets are icy bodies from the cold outer solar system that grow glowing comas and tails when the Sun’s heat vaporises their ice. In short, asteroids are dirty rocks and comets are dirty snowballs, though the line between them can blur.

How many asteroids are there in the asteroid belt?

The main belt contains an estimated 1 to 2 million asteroids larger than one kilometre across, plus many millions of smaller ones. More than 1.3 million have been catalogued and given orbits as of 2026, yet they only add up to about 4 percent of the Moon’s mass, so the belt is far emptier than it sounds.

Can you see asteroids with a telescope or binoculars?

Yes. Vesta can reach naked-eye visibility under dark skies, and both Vesta and Ceres are easy binocular targets near opposition. A small telescope reveals several more, though they look like faint stars — you confirm them by tracking their motion against the background stars from one night to the next.

What is the largest asteroid?

Ceres is the largest object in the asteroid belt at about 939 kilometres across, large enough to be classified as a dwarf planet. It holds roughly a third of the belt’s total mass. The next largest are Vesta and Pallas, each around 510 to 525 kilometres in diameter.

Are near-Earth asteroids dangerous?

Most near-Earth asteroids pose no threat, and NASA has ruled out any significant impact risk from known objects for the next hundred years. The real concern is undiscovered objects, which is why sky surveys and missions like DART — which successfully altered an asteroid’s orbit in 2022 — are developing our ability to detect and deflect any future threat.

Trans-Neptunian objects are icy worlds that orbit the Sun beyond Neptune, in the frigid, dimly lit frontier of our solar system that includes the Kuiper Belt, the scattered disc, and the distant Oort Cloud. They range from city-sized chunks of frozen rock to dwarf planets larger than 2,000 kilometres across, and together they preserve a 4.6-billion-year-old record of how the planets formed.

I have been imaging the night sky since 2008, and these distant ice worlds are among the most humbling targets I know. From my remote rig at Deepsky Chile — an Alluna 12.5″ Ritchey–Chrétien on a Paramount MX+ — a 20th-magnitude dwarf planet shows up as nothing more than a faint dot that creeps across a star field over several nights. That dot, though, is a whole world billions of kilometres away. This guide explains what trans-Neptunian objects are, how the icy outer solar system is structured, which TNOs matter most, how they were discovered, and whether you can capture them yourself.

What is a trans-Neptunian object?

A trans-Neptunian object is any minor planet or dwarf planet in the solar system whose average orbital distance from the Sun is greater than Neptune’s. Neptune orbits at about 30 astronomical units (AU), where one AU is the Earth–Sun distance, so everything orbiting beyond roughly 30 AU qualifies.

These bodies are overwhelmingly made of frozen volatiles — water ice, methane, ammonia, and nitrogen ices — mixed with rock. They formed in the cold outer regions of the protoplanetary disc and never gathered enough material to become full planets. Because they have stayed deep-frozen for billions of years, they are close to pristine relics of the early solar system.

The first TNO ever found was Pluto, discovered in 1930. For more than six decades it was thought to be alone out there. Then in 1992 astronomers found a second object, 1992 QB1, confirming that Pluto was simply the brightest member of a vast population. Today more than 5,000 trans-Neptunian objects are catalogued, and statistical models suggest hundreds of thousands larger than 100 km still await discovery.

Why do they matter to astronomers?

TNOs matter because they are time capsules. The inner planets were heated, melted, and reshaped; the icy bodies beyond Neptune were not. Studying their composition, colours, and orbits lets scientists reconstruct how the giant planets migrated and how the solar system settled into its current architecture.

What is the Kuiper Belt?

The Kuiper Belt is a doughnut-shaped ring of icy bodies that extends from Neptune’s orbit at about 30 AU out to roughly 50 AU from the Sun. It is the most populated reservoir of trans-Neptunian objects and the source region for many short-period comets.

Named after astronomer Gerard Kuiper, the belt holds the majority of well-studied TNOs, including all four belt-resident dwarf planets. NASA describes it as the solar system’s “third zone,” lying beyond the rocky inner planets and the gas-giant outer planets. You can read more in NASA’s Kuiper Belt overview.

Within the belt, objects fall into a few dynamical families:

• Classical Kuiper Belt objects (“cubewanos”) — bodies on relatively circular, stable orbits that do not strongly interact with Neptune. 1992 QB1 is the prototype.
• Resonant objects — bodies locked in orbital resonance with Neptune. Pluto sits in the 2:3 resonance (two orbits for every three of Neptune’s), so these are nicknamed “plutinos.”
• Cold and hot populations — the “cold” group has low orbital inclinations and reddish colours, hinting it formed in place; the “hot” group has tilted, stirred-up orbits.

How is the icy outer solar system structured?

The icy outer solar system is layered into three broad zones: the Kuiper Belt, the scattered disc, and the Oort Cloud, each progressively farther out and more loosely bound to the Sun.

Understanding these zones is the key to making sense of where any given TNO lives. They overlap at their edges, but each has a distinct character.

What is the difference between the Kuiper Belt and the scattered disc?

The Kuiper Belt holds objects on fairly stable orbits between about 30 and 50 AU, while the scattered disc holds objects flung onto highly elongated, tilted orbits that can carry them far beyond 50 AU. Scattered-disc objects were gravitationally “scattered” outward by Neptune long ago.

Eris — the most massive TNO known — is a scattered-disc object. Its orbit swings out to nearly 97 AU at its farthest. The scattered disc is also considered the main source of short-period comets such as those in the Jupiter family.

What is the Oort Cloud?

The Oort Cloud is a hypothesised spherical shell of icy bodies surrounding the entire solar system at distances of thousands to perhaps 100,000 AU. It is the presumed source of long-period comets, and no Oort Cloud object has ever been directly imaged in place.

Sedna is often cited as a possible link between the scattered disc and the inner Oort Cloud. Its enormous orbit takes roughly 10,500 years to complete and never brings it close to Neptune, so something other than Neptune must have placed it there.

What are the largest trans-Neptunian objects?

The largest trans-Neptunian objects are the dwarf planets Pluto and Eris, followed by Haumea, Makemake, and Gonggong, all measuring more than 1,000 kilometres across. These are the giants of the icy outer solar system, though even the biggest is smaller than Earth’s Moon.

Here is how the heavyweights compare. Pluto edges out Eris in diameter, but Eris is actually about 27% more massive — a reminder that these worlds differ in density as well as size.

Pluto: the original trans-Neptunian object

Pluto is the largest known TNO at roughly 2,377 km across and the first to be discovered. The 2015 flyby by NASA’s New Horizons spacecraft revealed nitrogen-ice glaciers, water-ice mountains, and a surprisingly active surface. For the full story of this world, see our dedicated guide to Pluto, the most famous dwarf planet.

Eris: the discovery that demoted Pluto

Eris, found in 2005, is the most massive TNO and the object that forced the International Astronomical Union to define the term “dwarf planet” in 2006 — the decision that reclassified Pluto. Learn more in our profile of Eris and how it reshaped the planet debate.

Haumea, Makemake, Sedna, and Arrokoth

Haumea is one of the strangest known worlds: it spins so fast (once every four hours) that it is stretched into an egg shape, and in 2017 it became the first TNO found to have rings. Makemake is a bright, frost-covered dwarf planet with a faint moon discovered in 2016.

Sedna is a distant, reddish world on one of the most extreme orbits known. Arrokoth, by contrast, is tiny — about 35 km end to end — but historically priceless: on 1 January 2019, New Horizons flew just 3,500 km past it, the most distant flyby of any object ever explored. Arrokoth turned out to be a primordial “contact binary,” two lobes that gently fused early in the solar system’s history.

How were trans-Neptunian objects discovered?

Trans-Neptunian objects were discovered by carefully comparing images of the same star field taken hours or nights apart and looking for the one faint point of light that moved against the fixed stars. Distant TNOs move very slowly, so the technique demands patience and precise instruments.

The history breaks down clearly:

1. 1930 — Clyde Tombaugh discovers Pluto using a blink comparator, flicking between photographic plates to spot motion.
2. 1992 — David Jewitt and Jane Luu find 1992 QB1, the first Kuiper Belt object after Pluto, opening the floodgates.
3. 2002–2007 — CCD survey cameras led by teams such as Mike Brown’s find Quaoar, Sedna, Haumea, Eris, Makemake, and Gonggong in quick succession.
4. 2014 — The Hubble Space Telescope identifies Arrokoth specifically as a flyby target for New Horizons.

Modern wide-field surveys now do the heavy lifting, and large new telescopes coming online in 2026 are expected to find thousands more faint TNOs, including possible new dwarf planets. The debate over a hypothetical “Planet Nine,” inferred from the clustered orbits of distant detached objects, keeps this region one of the most actively searched in astronomy.

Can amateur astronomers observe or image TNOs?

Yes — a few of the brightest trans-Neptunian objects are within reach of amateur equipment, but the vast majority are far too faint for visual observation and demand long-exposure imaging. This is genuinely advanced-level deep-sky work.

The practical reality comes down to brightness. Here is roughly what you are up against:

• Pluto (~magnitude 14.4) — the easiest target. An 8–10″ telescope under dark skies can show it visually as a faint star, and any reasonable astrophotography setup can capture it.
• Makemake (~16.7), Haumea (~17.3) — imaging targets needing larger apertures and stacked exposures.
• Eris (~18.7), Gonggong, Sedna (~20.5+) — require serious aperture, dark skies, and careful stacking; Sedna is at the edge of what advanced amateurs can record.

How do you confirm you actually imaged a TNO?

You confirm a TNO by imaging the same field on two or more nights and identifying the single “star” that has shifted position. Because TNOs are so distant, the motion is small — often just a few arcseconds per night — so you need accurate plate-solving and a planetarium app that plots the object’s predicted track.

From my own experience, Pluto is a satisfying first attempt: a couple of 60-second sub-exposures a night apart, blinked in software, and the planet quietly betrays itself by moving. For anything fainter, I rely on the dark Atacama skies and the long focal length of the Alluna RC at Deepsky Chile, stacking many sub-exposures to drag a 19th- or 20th-magnitude dot out of the noise. If you want to plan brightness and exposure properly, our astrophotography calculators can help you work out realistic sub-exposure times for faint targets.

Practical tips for imaging faint outer-solar-system objects

• Shoot from the darkest site you can reach; sky glow buries faint TNOs faster than anything.
• Use a mono camera with no filter (luminance) to maximise signal on these colourless dots.
• Plan around opposition, when the object is closest, highest, and brightest.
• Keep your field consistent night to night so blinking the frames is straightforward.
• Plate-solve every frame so you can overlay the object’s ephemeris precisely.

How do TNOs fit into the wider solar system?

Trans-Neptunian objects represent the icy outer third of the solar system, the population that bridges the gap between the planets we can easily see and the comet reservoirs that occasionally visit the inner system. They are deeply connected to the worlds nearer home.

Many short-period comets originate among scattered-disc TNOs, perturbed inward until the Sun’s heat boils off their ices into glowing tails. The rocky asteroids of the inner system are their warmer, drier cousins. And the migration of giant planets like Jupiter early in solar-system history is precisely what sculpted the Kuiper Belt and scattered disc into the shapes we map today. For the bigger picture, our complete solar system guide ties all these regions together, and our overview of the dwarf planets and the major planets puts the TNO dwarf worlds in context.

For an authoritative scientific reference, Britannica’s entry on the Kuiper Belt is a reliable starting point, and the IAU’s dwarf-planet definitions explain exactly where the largest TNOs sit in the official taxonomy.

Frequently asked questions

What is the difference between a Kuiper Belt object and a trans-Neptunian object?

A trans-Neptunian object is any body orbiting beyond Neptune, while a Kuiper Belt object is the subset of TNOs that live specifically in the Kuiper Belt between about 30 and 50 AU. All Kuiper Belt objects are TNOs, but scattered-disc and Oort Cloud bodies are TNOs that lie outside the belt.

Is Pluto a trans-Neptunian object?

Yes. Pluto is the largest and first-discovered trans-Neptunian object. It is a dwarf planet orbiting in the Kuiper Belt in a 2:3 orbital resonance with Neptune, which is why Pluto and similar objects are nicknamed “plutinos.”

What is the largest trans-Neptunian object?

Pluto is the largest TNO by diameter at about 2,377 km, just ahead of Eris at roughly 2,326 km. However, Eris is the most massive TNO, with about 27% more mass than Pluto despite being slightly smaller in volume.

How many trans-Neptunian objects are there?

More than 5,000 TNOs have been catalogued so far, but astronomers estimate there are hundreds of thousands larger than 100 km, plus possibly trillions of comet-sized bodies in the Kuiper Belt and Oort Cloud combined. New surveys in 2026 are expected to find many more.

Can you see trans-Neptunian objects with a telescope?

Only the brightest, such as Pluto at about magnitude 14, are realistically within reach of amateur telescopes, and even Pluto looks like a faint star. Most TNOs require long-exposure astrophotography with large apertures and multi-night imaging to confirm their slow movement against background stars.

The eight planets of the solar system, in order from the Sun, are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. This guide walks through every planet — what it is, how to find it in the night sky, and how to photograph it — plus where dwarf planets like Pluto fit in. It is the hub for our full solar system series.

What are the planets of the solar system in order?

The planets of the solar system orbit the Sun in two clear groups. The four inner planets — Mercury, Venus, Earth, and Mars — are small, rocky worlds. The four outer planets — Jupiter, Saturn, Uranus, and Neptune — are giant balls of gas and ice. Here is the order of the planets from the Sun outward:

1. Mercury — the smallest planet and the closest to the Sun.
2. Venus — the hottest planet, wrapped in thick clouds; the brightest object in our sky after the Sun and Moon.
3. Earth — our home, the only world known to host life.
4. Mars — the rusty red planet and a favourite small-telescope target.
5. Jupiter — the largest planet, with its Great Red Spot and four bright Galilean moons.
6. Saturn — the ringed jewel of the solar system.
7. Uranus — a pale ice giant tipped on its side.
8. Neptune — the windiest, most distant planet from the Sun.

A simple way to remember the order of the planets is the mnemonic “My Very Educated Mother Just Served Us Nachos” — the first letter of each word matches a planet in sequence.

How many planets are in the solar system?

There are eight planets in the solar system. For most of the 20th century the count was nine, but in 2006 the International Astronomical Union adopted a formal definition of a planet. To qualify, a body must orbit the Sun, be massive enough to pull itself into a round shape, and have “cleared its neighbourhood” of other debris. Pluto fails the third test, so it was reclassified as a dwarf planet alongside worlds such as Eris, Haumea, Makemake, and Ceres.

That change did not remove anything from the sky — it simply tidied up our categories as we discovered more icy bodies in the trans-Neptunian region beyond Neptune.

What separates the inner planets from the outer planets?

The dividing line is the asteroid belt between Mars and Jupiter, but the deeper reason is the “frost line” in the young solar system. Close to the Sun it was too hot for ices to survive, so only rock and metal could clump together — producing small, dense, slow-forming terrestrial planets. Beyond the frost line, water, ammonia, and methane froze solid, giving the outer planets vastly more material to gather. They grew massive enough to hold onto hydrogen and helium gas, becoming the giants we see today.

This is why the inner planets are small and rocky with few or no moons, while the outer planets are enormous, gas-rich, and surrounded by ring systems and dozens of moons. It also explains the temperature gradient: Mercury bakes at over 400°C in daylight, while Neptune sits at around −200°C.

What are the inner (terrestrial) planets?

The four inner planets are dense, rocky worlds with solid surfaces. They are the easiest planets for a beginner to recognise because Venus and Mars in particular shine brightly to the naked eye.

Mercury

Mercury is the smallest planet and never strays far from the Sun in our sky, so it is best caught low on the horizon at dawn or dusk during a greatest elongation. Through a telescope it shows phases like a tiny Moon. See our dedicated Mercury observing guide for elongation dates and imaging tips.

Venus

Venus is the brightest planet and is unmistakable as the “morning star” or “evening star.” A small telescope reveals its crescent-to-gibbous phases, though its blinding glare and featureless cloud deck make detail hard to capture without a UV filter.

Earth

Our own planet is the benchmark for everything else — the only world with liquid water oceans and a breathable atmosphere on its surface. Understanding Earth’s tilt and orbit explains the seasons and why some planets are better placed for viewing at certain times of year.

Mars

Mars is the red planet, and every 26 months it reaches opposition, when it is closest and brightest. Near opposition a modest telescope can reveal its polar ice caps and dark surface markings. Our Mars observing guide covers the opposition cycle and how to time your imaging.

What are the outer planets — the gas and ice giants?

The four outer planets are enormous compared with Earth and have no solid surface to stand on. Jupiter and Saturn are gas giants; Uranus and Neptune are colder ice giants. They are the most rewarding planets for astrophotography because they show genuine detail.

Jupiter

Jupiter is the largest planet — more massive than all the others combined. Even a small telescope shows its two main cloud belts and the ever-changing dance of its four Galilean moons. Read the full Jupiter guide for how to capture the Great Red Spot.

Saturn

Saturn is the showpiece of the solar system. The moment a beginner first sees its rings through an eyepiece is unforgettable. Our Saturn guide explains the ring tilt cycle and how to photograph the Cassini Division.

Uranus and Neptune

Uranus and Neptune are faint, distant ice giants. Uranus is just visible to the naked eye from a dark site as a dim “star,” while Neptune always needs binoculars or a telescope. In images they appear as tiny blue-green discs — a satisfying challenge once you have mastered the brighter planets.

Where do dwarf planets, moons, and small bodies fit in?

The eight planets share the solar system with a huge cast of smaller objects. Dwarf planets such as Pluto and Eris are round but have not cleared their orbits. The moons of the solar system number over 290, from our own Moon to Jupiter’s volcanic Io. Rocky asteroids cluster mainly between Mars and Jupiter, while icy comets swing in from the outer solar system and occasionally light up our skies. Debris from comets also produces the annual meteor showers.

Could there be a ninth planet?

Although there are eight official planets, some astronomers suspect a large, undiscovered world — nicknamed “Planet Nine” — may orbit far beyond Neptune. The idea comes from the strangely clustered orbits of several distant trans-Neptunian objects, which look as though something massive is shepherding them. If it exists, Planet Nine could be five to ten times Earth’s mass and take thousands of years to circle the Sun.

So far it has not been found, and a new generation of professional survey telescopes is expected to settle the question this decade. For now, eight remains the official count — but the solar system may still hold surprises at its dark, distant edge.

How do you observe and photograph the planets?

Planetary imaging is one of the most accessible branches of astrophotography — you can do it from a light-polluted city because the planets are bright. In my own imaging from a remote rig in the Atacama and from suburban backyards, the planets are where most people get their first “wow” result.

The technique differs from deep-sky work. Instead of long exposures, planetary imagers shoot high-frame-rate video and stack the sharpest frames — a method called “lucky imaging” that beats atmospheric turbulence. A few practical pointers:

• Use enough focal length. Planets are tiny, so you want a long effective focal length — often with a Barlow lens. Check your image scale and framing first with our telescope field of view calculator.
• Shoot at opposition. Each planet is biggest and brightest near opposition; plan your sessions around those dates.
• Image when the planet is high. The higher a planet sits, the less atmosphere you look through and the sharper it appears.
• Plan your wider setup. For multi-target nights, the astrophotography calculator helps you balance pixel scale, sampling, and exposure.

Jupiter, Saturn, and Mars are the best planets for beginners because they reveal real detail. Venus and Mercury are interesting for their phases, while Uranus and Neptune are advanced targets best left until your tracking and focus are dialled in.

When is the best time to see the planets?

Each planet has its own ideal viewing window, driven by where it sits relative to Earth and the Sun:

• Outer planets (Mars, Jupiter, Saturn, Uranus, Neptune) are best at opposition, when Earth passes directly between the planet and the Sun. The planet then rises at sunset, stays up all night, and is at its closest and brightest.
• Inner planets (Mercury and Venus) never reach opposition because they orbit closer to the Sun than we do. Instead, look for them at greatest elongation, when they appear farthest from the Sun in the sky — low in the west after sunset or the east before dawn.

A planet is sharpest when it is high overhead, so favour the hours around when it crosses the meridian. Conjunctions — when two planets, or a planet and the Moon, appear close together — make striking wide-field photos and are worth tracking on an astronomy app or almanac. Because the planets move against the background stars from night to night, no two observing seasons are quite the same, which is part of what keeps planetary observing endlessly rewarding.

If you are planning a session, decide your target first, confirm it is well placed for your latitude and date, then use the FOV simulator to preview exactly how it will sit in your eyepiece or camera frame.

Quick planet facts

Here is an at-a-glance comparison of the eight planets, ordered from the Sun:

Frequently asked questions about the planets

What are the 8 planets in order from the Sun?

The eight planets in order from the Sun are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. The first four are rocky terrestrial planets and the last four are giant planets.

Why is Pluto no longer a planet?

Pluto was reclassified as a dwarf planet in 2006 because it has not cleared its orbital neighbourhood of other icy bodies, failing one of the three conditions in the IAU’s definition of a planet.

What is the largest planet in the solar system?

Jupiter is the largest planet. It is so big that more than 1,300 Earths could fit inside it, and it is more massive than all the other planets put together.

Which planets can you see without a telescope?

Five planets are visible to the naked eye: Mercury, Venus, Mars, Jupiter, and Saturn. Venus and Jupiter are especially bright, while Uranus and Neptune require binoculars or a telescope.

What is the best planet to photograph for beginners?

Jupiter and Saturn are the best planets for beginners. They are bright, show obvious detail (cloud belts, moons, and rings), and respond well to the high-frame-rate “lucky imaging” technique even from the city.

Keep exploring the solar system

Now that you know the planets of the solar system in order, dive deeper into individual worlds and the small bodies that share their space. Start with the giants — Jupiter and Saturn — then branch out to Mars, the dwarf planets, and the rest of our solar system hub. When you are ready to image them, our free field of view simulator will show you exactly how each planet frames in your gear.

By Hamza — astrophotographer since 2008, imaging from a remote dark-sky rig at Deepsky Chile.

Quick answer: Is Pluto a planet? No — Pluto is a dwarf planet. The International Astronomical Union (IAU) reclassified it on August 24, 2006, because it fails one of the three planet rules: it has not cleared its orbital neighborhood. Pluto still orbits the Sun and is round, but it shares its space with countless icy bodies in the Kuiper Belt.

Pluto is the most famous “demoted” world in the solar system, and the question “is Pluto a planet?” still sparks arguments at dinner tables, in classrooms, and even at NASA. The short version: for 76 years Pluto was counted as the ninth planet, but in 2006 astronomers agreed on a strict definition of the word planet for the very first time — and Pluto did not make the cut. It became the best-known member of a category called dwarf planets, joining worlds like Eris, Ceres, Haumea, and Makemake.

This guide answers every common Pluto question in plain language, then goes somewhere almost no other page does: how to actually find and photograph Pluto yourself. You will get the answer-first verdict, the full reclassification story (including the live 2026 “make Pluto a planet again” debate), a scannable quick-facts table, the truth about its size compared to the Moon, its five moons, what the New Horizons flyby discovered in 2015, and a hands-on observing section drawn from my own nights chasing this faint, star-like world through the eyepiece and the camera.

Pluto sits far out in the Kuiper Belt, the ring of frozen leftovers beyond Neptune, which is exactly why it never swept its lane clean. For the bigger picture of how Pluto fits among its icy siblings, see our complete guide to dwarf planets in the solar system, part of the broader Solar System hub. If you are mainly here to settle the planet debate once and for all, keep reading — the next section breaks down the three IAU rules one by one.

Table of contents

1. Is Pluto a planet?
2. Why is Pluto not a planet anymore?
3. Will Pluto ever be a planet again?
4. Pluto facts: size, distance, orbit and temperature
5. Pluto’s moons: Charon and the rest
6. What New Horizons revealed (2015)
7. How Pluto was discovered
8. How to see and photograph Pluto
9. Frequently asked questions

Is Pluto a planet?

No. Pluto is not one of the eight planets. Since August 24, 2006, the International Astronomical Union (IAU) has classified Pluto as a dwarf planet — a real category of its own, not a “fake” planet. It still orbits the Sun and it is still round. It simply does not meet every rule the IAU uses to define a full-fledged planet.

To count as a planet under IAU Resolution 5A, a body must pass all three of these tests:

Pluto sails through the first two with no trouble. It is the third rule it fails — and that single failure is the entire reason it is a dwarf planet instead of a planet.

What does “clearing the neighborhood” mean? A true planet is the gravitational boss of its orbital lane. Over billions of years, it has swept up, flung away, or captured nearly every other object near its path, so it orbits more or less alone. Earth has done this. So has Neptune. Pluto has not. It lives inside the Kuiper Belt, a vast ring of icy bodies beyond Neptune, and it shares that space with countless similar objects. In fact, Pluto’s mass is only a tiny fraction of the other material sharing its orbital zone, so its gravity is far too weak to dominate that crowd — it has never become the master of its own orbit.

Think of it this way: a planet is like the only large fish in its stretch of river. Pluto is one fish among thousands of others near its size — it just happens to be one of the bigger ones in a very crowded zone.

What is a dwarf planet, exactly?

A dwarf planet is a body that is round (its own gravity has pulled it into a sphere) and orbits the Sun, but has not cleared the other objects out of its orbital path. That last part is the whole difference between a dwarf planet and a planet. Dwarf planets are also not moons — they orbit the Sun directly, not another world.

The IAU currently recognizes five official dwarf planets:

Notice the pattern: four of the five dwarf planets live in the cold, crowded trans-Neptunian region beyond Neptune. Ceres is the lone exception — it sits much closer to us in the asteroid belt. So it is a common mistake to think every dwarf planet is a Kuiper Belt object; Ceres breaks that rule.

That is why the answer to both “is Pluto a planet?” and “is Pluto a dwarf planet?” is the same: Pluto is a dwarf planet, and the largest one out in the Kuiper Belt. To see how it stacks up against the others, visit our full guide to the solar system’s dwarf planets, and explore where Pluto fits within the wider Solar System hub.

Why is Pluto not a planet anymore?

Pluto is not a planet anymore because, in 2006, astronomers wrote the first official definition of the word “planet” — and Pluto did not meet all of it. Pluto stopped being a planet on August 24, 2006, the day the International Astronomical Union (IAU) passed Resolution 5A on the definition of a planet at its General Assembly in Prague.

The whole thing started with a discovery. In 2005, astronomer Mike Brown and his team announced Eris, a distant icy world out past Neptune. Eris was roughly the same size as Pluto, and it was actually more massive — about 27% heavier. That created a problem nobody could ignore: if Pluto counts as a planet, then Eris has to count too — and so do the other Pluto-sized objects astronomers were starting to find in the same region. Either the solar system was about to gain a 10th, 11th, and 12th planet, or the word “planet” needed a real, agreed-upon meaning. (Eris was the trigger for the whole debate, and it gets its own page in our look at Eris, the dwarf planet that demoted Pluto.)

So the IAU set three tests. To be a full planet, an object must:

Pluto passed the first two easily. It failed the third — and that one rule is the entire reason for its demotion.

What does “clearing the neighborhood” mean? It means a planet has to be the gravitational boss of its orbit. Over billions of years, a true planet either sweeps up the smaller objects near its path, flings them away, or locks them into orbit as moons. The result is a clean lane with one dominant body. Earth has done this. So has Neptune.

Pluto has not. It lives in the Kuiper Belt, a crowded ring of countless icy bodies beyond Neptune, and it shares that broad trans-Neptunian region with many neighbors — including Eris, which orbits even farther out in the scattered disc. Pluto simply isn’t massive enough to dominate its surroundings; for comparison, Earth outweighs everything else in its orbital zone by about 1.7 million times, while Pluto barely outweighs the debris around it. Because it shares its lane instead of ruling it, Pluto became a dwarf planet rather than a planet. You can read more about its crowded home region in our guide to the Kuiper Belt and trans-Neptunian objects.

Who actually decided this — and was it fair? The vote was made by the IAU, the only body with the authority to officially name and classify objects in space. But the decision was contentious. It happened on the final day of a roughly two-week meeting, after many attendees had already left, so only 424 astronomers — a small fraction of the IAU’s roughly 9,000 members — actually cast a ballot. Critics still point to that small turnout as a reason the result feels unsettled. Some astronomers — most vocally New Horizons lead scientist Alan Stern — argued the definition was flawed and never accepted it. That disagreement is exactly why the “is Pluto a planet?” question still flares up today. But as a matter of official record, the answer has not changed since 2006: Pluto is a dwarf planet. For the bigger picture, head back up to the Solar System hub or the parent guide to the dwarf planets of the solar system.

Will Pluto ever be a planet again?

Short answer: not officially, and no reversal is expected anytime soon. Pluto is still a dwarf planet under the only definition that counts for scientific naming — the International Astronomical Union’s (IAU) 2006 ruling. The IAU has never revisited or reversed that vote, and as of 2026 it has given no signal that it plans to. So while the argument is very much alive in public, Pluto’s status on the books has not changed.

That said, the debate is real, and serious scientists are on the “planet” side.

The competing “geophysical” definition. New Horizons mission lead Alan Stern and a group of planetary scientists reject the IAU rule and back a geophysical planet definition instead. Their idea is simple: if a body in space is big enough that its own gravity pulls it into a round (or nearly round) shape, and it is not a star, it is a planet. Under that “round = planet” test, Pluto qualifies easily — and so would dozens of other worlds, including large moons like our own Moon.

Why they say the IAU definition is flawed. Critics make a few recurring arguments:

Supporters of the IAU rule counter that “orbital dominance” is exactly what separates the eight major planets from the swarm of smaller Kuiper Belt bodies — and that a definition giving us 100-plus planets would be far less useful for teaching and science. (See how this plays out in the three IAU planet criteria and what “clearing the neighborhood” really means.)

Public and political pushback. Roughly every few years the topic flares up again — in op-eds, at conferences, in state legislatures (New Mexico in 2007 and Illinois in 2009 symbolically “kept” Pluto a planet), and most recently in late April 2026. Testifying before a U.S. House Appropriations subcommittee on April 28, 2026, NASA Administrator Jared Isaacman said he is “very much in the camp of ‘make Pluto a planet again.'” He added that NASA is “doing some papers right now” on a position it would “love to escalate through the scientific community to revisit this discussion” — and tied the effort to making sure Clyde Tombaugh, Pluto’s discoverer, “gets the credit he received once and rightfully deserves to receive again.” These moments generate headlines, but none carries the authority to change anything. Only the IAU can redefine “planet,” and it has not moved.

For most planetary scientists, the honest takeaway is this: the label is a human convention, but Pluto itself — a complex, geologically active world with mountains, glaciers, and a possible subsurface ocean — is fascinating regardless of which box we file it in. Explore where it sits among the other dwarf planets, the world whose discovery Eris triggered the whole debate, and the wider Solar System.

Pluto facts: size, distance, orbit and temperature

Here is the fast version of Pluto by the numbers. Every figure below is rounded to the values most scientists use today, drawn from NASA and New Horizons data.

How big is Pluto? Pluto is about 2,377 km (1,477 mi) across. That sounds large until you compare it to home. Pluto is smaller than Earth’s Moon and only about two-thirds the Moon’s width. It is roughly one-fifth the diameter of Earth. If Earth were a basketball, Pluto would be about the size of a golf ball. Its small size and shared orbit are the reasons it sits in the dwarf-planet club rather than with the major planets.

Pluto vs the Moon (size at a glance):

So Pluto is roughly two-thirds the width of our own Moon — a fact that surprises almost everyone, because for decades we pictured it as a full-sized ninth planet.

How far is Pluto? On average, Pluto orbits about 39.5 AU from the Sun. One AU (astronomical unit) is the Earth-Sun distance, so Pluto sits roughly 39.5 times farther out than we do — about 5.9 billion km (3.7 billion mi). Its orbit is also stretched and tilted, swinging from 29.7 AU at its closest to 49.3 AU at its farthest. For about 20 years (1979 to 1999) this carried Pluto inside Neptune’s orbit, making it temporarily the eighth-most-distant body from the Sun. Sunlight is so weak out there that noon on Pluto looks like deep twilight on Earth, and that same faintness is why you need real aperture to spot it (see the observing and astrophotography section below).

How cold is Pluto? Brutally cold. Surface temperatures average around -229°C (-380°F), just 44 degrees above absolute zero, and across the globe they run roughly -226°C to -240°C (-375°F to -400°F). At that chill, gases we breathe freeze solid — Pluto’s “snow” and surface frost are nitrogen, methane and carbon-monoxide ice. The temperature is not fixed, though. Because Pluto’s orbit is so eccentric, it warms slightly near closest approach and cools as it retreats. That swing drives a remarkable cycle: Pluto’s thin nitrogen atmosphere puffs up when it is nearer the Sun and partly freezes back onto the surface as it moves away. Pluto reached its closest point to the Sun (perihelion) back in 1989 and has been slowly receding ever since, heading toward its farthest point (aphelion) around the year 2113. Because it is moving outward the whole time, Pluto is expected to keep cooling and its atmosphere to keep thinning for decades to come.

A quick orbital oddity worth knowing: Pluto’s ~248-year trip around the Sun never actually crashes into Neptune. The two are locked in a 3:2 orbital resonance — Pluto completes two laps for every three Neptune makes — which keeps them safely out of each other’s way. You can place Pluto in its deep-freeze home region in the guide to trans-Neptunian objects and the Kuiper Belt, or step back up to the full dwarf planets guide and the Solar System hub for the bigger picture.

Pluto’s moons: Charon and the rest

Pluto has five known moons. From largest to smallest, they are Charon, Hydra, Nix, Kerberos, and Styx. Charon is by far the biggest; the other four are small, lumpy worlds discovered between 2005 and 2012, in the run-up to the New Horizons flyby.

Charon: about half the width of Pluto

Charon is so large compared to Pluto that the pair behaves almost like a double planet. Charon’s diameter is about 1,212 km (753 mi) — roughly half of Pluto’s 2,377 km (1,477 mi). No other moon in the solar system is anywhere near that big relative to the world it orbits. James Christy discovered it in 1978.

That size has a striking effect. The two bodies are mutually tidally locked, meaning each always shows the same face to the other. If you stood on the side of Pluto that faces Charon, the moon would hang frozen in the sky, never rising or setting. From the far side, you would never see Charon at all.

Stranger still, Pluto and Charon orbit a shared center of mass — the barycenter — that sits in empty space above Pluto’s surface, not deep inside Pluto. In every other planet–moon pair in our solar system, the barycenter lies inside the larger body, so the moon clearly circles the planet. Here, both worlds visibly swing around an external point. That is why many astronomers describe Pluto and Charon as a binary system.

The four small moons

The remaining moons are tiny, irregular, and oddly behaved. Rather than spinning smoothly, Nix and Hydra tumble chaotically as they orbit the shifting Pluto–Charon gravity field — Hubble observations showed they wobble so unpredictably that an observer would not see the same face twice.

All five names tie back to the Greek and Roman mythology of the underworld, fitting for a world named after its ruler. The four small moons are far too faint for backyard telescopes — even spotting Pluto itself is a real challenge, as covered in the observing Pluto section. For the wider family of icy worlds Pluto belongs to, see the guide to dwarf planets and the Kuiper Belt and trans-Neptunian objects.

What New Horizons revealed (2015)

For 85 years after Clyde Tombaugh found it, Pluto stayed a fuzzy dot. Even the Hubble Space Telescope showed only blurry patches of light and dark. That changed on July 14, 2015, when NASA’s New Horizons spacecraft raced past Pluto at about 49,600 km/h (30,800 mph) and gave us our first close-up look at this distant world. At closest approach, it came within about 12,500 km (7,800 mi) of Pluto’s surface.

What it found stunned everyone. Scientists expected a dead, cratered ball of ice. Instead, Pluto turned out to be a complex, active, planet-like world.

The headline discoveries

Cryovolcanism: a world that may still erupt

One of the most surprising finds was cryovolcanism — volcanoes that erupt icy slush instead of molten rock. The leading candidates are two enormous mounds south of the heart, Wright Mons and Piccard Mons, each roughly 160 km (100 mi) across and about 4 km (13,000 ft) high, with a deep central depression like a caldera. The bumpy, crater-poor ground around them looks like it was built by repeated outpourings of water-ice “lava” within roughly the last billion or two years — recent, in geological terms. If confirmed, it means Pluto still has internal heat, which strengthens the case for that hidden subsurface ocean.

A 2026 freshness note: Pluto’s haze “thermostat”

Pluto keeps making news. Recent observations with the James Webb Space Telescope (JWST) confirmed that Pluto’s high-altitude haze — those blue layers New Horizons photographed — actually controls the dwarf planet’s climate. The tiny haze particles soak up sunlight by day and radiate heat away at night, cooling Pluto’s upper atmosphere far more than its gases alone could (by roughly 30°C more than older models predicted). Scientists call it a haze “thermostat,” and it appears to be unique in the solar system. It is a striking reminder that even a “demoted” world a few billion kilometers away is still teaching us new physics.

Why it rewrote what we knew

Before 2015, most people pictured dwarf planets as boring frozen rubble. New Horizons proved that small, far-off worlds can have flowing glaciers, towering mountains, layered skies, possible ice volcanoes, and maybe even hidden oceans. A body does not need to be a “real” planet to be fascinating and active.

The flyby also gave Pluto a face. The heart, the glacier, and the haze turned an abstract debate about classification into a real place people care about. That emotional pull feeds today’s renewed “make Pluto a planet again” arguments.

You can read NASA’s full mission story at the New Horizons mission page and NASA’s Pluto overview. For more on the icy region Pluto calls home, see our guide to trans-Neptunian objects and the Kuiper Belt, and head back up to the dwarf planets overview to see how Pluto compares with its siblings.

How Pluto was discovered

Clyde Tombaugh discovered Pluto on February 18, 1930, at Lowell Observatory in Flagstaff, Arizona. He was a 24-year-old farm boy from Kansas with no college degree, hired to do one tedious job: hunt for “Planet X.”

That search began with Percival Lowell. The wealthy astronomer was convinced an unseen ninth planet was tugging on the orbits of Uranus and Neptune, and he spent his final years predicting where it should be. Lowell died in 1916 without finding it. More than a decade later, the observatory he founded handed the hunt to Tombaugh.

Tombaugh’s method was slow and brilliant. He photographed the same patch of sky on different nights, then loaded pairs of plates into a blink comparator — a machine that flips back and forth between two images. Stars stay put; a planet shifts position. On February 18, 1930, Tombaugh compared two plates taken in January 1930 (on the 23rd and the 29th) and spotted one faint speck that jumped between them. He had found a new world far beyond Neptune.

The name came from an 11-year-old English schoolgirl, Venetia Burney. Over breakfast, she suggested “Pluto,” the Roman god of the underworld — a fitting title for a dark, frozen world. Her grandfather passed the idea to Lowell Observatory, and it was made official on May 1, 1930. A nice bonus: the first two letters, PL, honor Percival Lowell’s initials. Walt Disney’s cartoon dog Pluto debuted later that same year, but the planet came first — the dog was almost certainly named after the headline-making discovery.

Tombaugh’s story has one last chapter. When he died in 1997, a small portion of his ashes was placed aboard NASA’s New Horizons spacecraft. On July 14, 2015, those ashes swept past Pluto — making Tombaugh the only person whose remains have traveled to a world he discovered. To explore where Pluto sits today, see our dwarf planets guide and the wider Solar System hub.

How to see and photograph Pluto

Pluto is hard. Right now it shines at only about magnitude 14.9–15 — and it sinks to magnitude ~15.0 around its July 2026 opposition — far too faint for your eyes alone or for binoculars. (The often-quoted “magnitude 14.4” is roughly its all-time brightest; at this point in its orbit, plan for fainter than that.) To have a realistic chance you want a 10-inch (250 mm) or larger telescope under genuinely dark skies. A skilled observer can sometimes pull Pluto out with an 8-inch (200 mm), but only under excellent, truly dark rural skies — treat 10–12 inches as the practical floor. Even then, do not expect a view of “the heart” or those icy mountains. Pluto never shows a disk. In any backyard telescope it looks exactly like a faint star: a single, dim point of light lost among thousands of others.

Observing difficulty: hard (expert). This is one of the toughest targets in the solar system for amateurs, mostly because Pluto hides in star-rich fields near the Milky Way and is dimming year by year as it recedes from the Sun. Remember the orbital picture from the facts section: Pluto passed perihelion in 1989 and is now heading outward toward aphelion around 2113, so it will keep fading for decades. In short, it is easier to catch now than it will be later — there is no reason to wait.

Because Pluto looks like every other faint star, the only way to prove you found it is to watch it move. Here is the method I use on my remote rig:

1. Plan the field. Pull a current finder chart or ephemeris — in 2026 Pluto sits in Capricornus — and aim for the weeks around opposition (about July 27, 2026), when Pluto is highest, closest, and at its best for the year.
2. Frame the star field. Use our FOV simulator to match your scope and camera to the exact patch of sky so Pluto lands cleanly on your sensor with reference stars around it.
3. Expose for a magnitude-15 dot. Pluto is faint, so each sub-exposure has to go deep without burning out the field stars. Our sub-exposure calculator helps you pick an exposure time that beats the read noise and sky glow. (Both tools live in the astrophotography calculator hub.)
4. Image two or more nights. Shoot the same field on at least two nights, 24+ hours apart.
5. Blink the frames. Flip between the aligned images. Every real star stays put; the one “star” that shifts position is Pluto. This blink-comparison trick is the same idea Clyde Tombaugh used to discover it in 1930, just with a screen instead of glass plates.

I confirm Pluto exactly this way from my dark-sky setup at Deepsky Chile (a 12.5-inch Ritchey-Chretien on a Paramount mount). The southern site and large aperture make the blink obvious within two clear nights. You can read more about that rig and my background on the about page. The payoff is not a pretty picture. It is the quiet thrill of catching a world 5.9 billion km (3.7 billion mi) away drifting against the stars with your own equipment.

Frequently asked questions

Is Pluto a planet?
No. Pluto is not a full planet. Since August 24, 2006, the International Astronomical Union (IAU) has classified Pluto as a dwarf planet. It is still a real, fascinating world — it just doesn’t meet all three of the IAU’s rules for a full-sized planet.

Why is Pluto not a planet?
Pluto fails one of the three IAU planet tests: it has not “cleared the neighborhood” around its orbit. A true planet is the gravitational boss of its orbital zone, but Pluto shares the Kuiper Belt with countless other icy objects. It passes the first two tests (it orbits the Sun, and it is round), but missing the third one is what makes it a dwarf planet.

When did Pluto stop being a planet, and who decided?
On August 24, 2006, at the IAU General Assembly in Prague. The IAU — the body that officially classifies objects in space — voted on Resolution 5A, which created the first official definition of a “planet,” and Pluto did not qualify. Only about 424 of the roughly 9,000 IAU members were present to vote, which is one reason critics still call the decision contested. Pluto had been counted as the ninth planet for 76 years, ever since its 1930 discovery.

Will Pluto become a planet again?
Maybe, but not yet. In late April 2026, NASA Administrator Jared Isaacman told a congressional hearing he is “very much in the camp of ‘make Pluto a planet again,'” and said NASA is working on papers to push the science community to revisit the question. Some scientists also favor a “geophysical” definition that would restore it. However, only the IAU can officially change the rules, and no vote has reversed the 2006 decision. As of 2026, Pluto remains a dwarf planet.

How big is Pluto?
Pluto is about 2,377 km (1,477 miles) across — roughly two-thirds (about 68%) the width of Earth’s Moon. That makes it smaller than the Moon, which spans 3,474 km (2,159 miles). It is the largest dwarf planet by diameter.

How far is Pluto from the Sun?
On average about 39.5 AU, or roughly 5.9 billion km (3.7 billion miles). Its orbit is very stretched, ranging from 29.7 AU at its closest to 49.3 AU at its farthest. From 1979 to 1999 it was actually closer to the Sun than Neptune.

How cold is Pluto?
Extremely cold — around −229°C (−380°F, or about 44 kelvin). At that temperature, gases like nitrogen and methane freeze solid into the ices that coat Pluto’s surface.

How long is a day and a year on Pluto?
A day on Pluto lasts about 6.4 Earth days (the time it takes to spin once, and it spins in a retrograde direction). A year — one full orbit around the Sun — takes about 248 Earth years.

How many moons does Pluto have?
Five. Charon is by far the largest (~1,212 km) and so big relative to Pluto that the two orbit a shared point in space, behaving almost like a binary system. The four small moons are Nix, Hydra, Kerberos, and Styx, all named from underworld mythology.

Why is it called Pluto?
An 11-year-old English schoolgirl named Venetia Burney suggested it in 1930, after Pluto, the Roman god of the underworld — a fitting name for a cold, dark, distant world. There was a bonus, too: the first two letters, “PL,” match the initials of Percival Lowell, the astronomer whose search led to the discovery. The name became official on May 1, 1930.

Is Pluto in the Kuiper Belt?
Yes. Pluto orbits within the Kuiper Belt, a vast ring of icy bodies beyond Neptune, and it is the largest known object there. Sharing that crowded region — rather than ruling it — is precisely why Pluto counts as a dwarf planet instead of a planet.

Does Pluto have an atmosphere and an ocean?
Yes to a thin atmosphere, and maybe to an ocean. Pluto has a thin atmosphere of mostly nitrogen, with some methane and carbon monoxide, that expands when Pluto is nearer the Sun and partly freezes onto the surface as it moves away. New Horizons also found evidence that a liquid water ocean may lie hidden beneath Pluto’s icy crust, kept from freezing by internal heat — though that subsurface ocean is still considered likely rather than proven.

What is Pluto made of?
Pluto is a mix of about two-thirds rock and one-third ice. Its surface is coated in frozen nitrogen, methane, and carbon monoxide, with mountains of hard water-ice. New Horizons even found hints of a possible liquid water ocean beneath the icy crust.

Who discovered Pluto?
American astronomer Clyde Tombaugh discovered Pluto on February 18, 1930, at Lowell Observatory in Arizona, using a blink comparator to spot its motion. It was named by 11-year-old Venetia Burney, after the Roman god of the underworld.

Has a spacecraft ever visited Pluto?
Yes. NASA’s New Horizons probe flew past Pluto on July 14, 2015, passing about 12,500 km (7,800 miles) above its surface. It revealed the bright, heart-shaped Tombaugh Regio, the vast Sputnik Planitia nitrogen-ice glacier, towering water-ice mountains, possible ice volcanoes, and a hazy, layered atmosphere.

Can you see Pluto with a telescope?
Yes, but it’s a serious challenge. Pluto shines at only about magnitude 14.9–15 (around magnitude 15.0 at its July 2026 opposition). In practice you’ll want a 10-inch (250 mm) or larger telescope under truly dark skies — an 8-inch can reach it only in excellent conditions — and even then it looks like a faint star with no disk. You confirm it by photographing or sketching it over several nights and watching it drift against the background stars. (Our observing-and-astrophotography guide above walks through the full method.)

Is Pluto bigger than Eris?
It depends on how you measure. Pluto is slightly larger in diameter (~2,377 km vs. Eris’s ~2,326 km), but Eris is about 27% more massive. Eris’s discovery in 2005 is what triggered the whole “what is a planet?” debate — you can read more on our Eris dwarf planet page.

Written by Hamza, an astrophotographer imaging the night sky since 2008. I chase faint targets like Pluto from a remote rig at Deepsky Chile — a 12.5-inch Ritchey-Chretien on a Paramount MX+ mount — and share the results on Instagram @stellar.nomads. More about my setup and approach is on the about page.

Ready to hunt Pluto yourself? Plan the exact star field with the FOV simulator, dial in your exposure with the sub-exposure calculator, and find every other tool you need in the astrophotography calculator hub. Then keep exploring: head back up to the dwarf planets guide, the main Solar System hub, or the Kuiper Belt and trans-Neptunian objects guide.

By Hamza — astrophotographer since 2008, imaging from a remote 12.5″ Ritchey-Chrétien at Deepsky Chile (@stellar.nomads)

Quick answer: A dwarf planet is a round body that orbits the Sun and has not cleared its orbital neighborhood of other objects, and is not a moon. The five bodies the IAU officially recognizes are Ceres, Pluto, Haumea, Makemake, and Eris — though astronomers suspect 100+ more await confirmation.

Dwarf planets are the Solar System’s in-between worlds: too big and too round to be mere asteroids, yet not dominant enough in their orbits to count as full planets. They include the largest object in the asteroid belt (Ceres), the famous demoted ninth planet (Pluto), and three frozen wanderers far beyond Neptune (Haumea, Makemake, and Eris). This page is the dwarf-planets hub within our larger Solar System guide, and it aims to be the single most useful resource on the topic anywhere on the web.

What sets this guide apart is the angle no science encyclopedia or general astronomy site offers: how to actually see and image these worlds. Alongside plain-English explanations of the science — what “clearing the neighborhood” really means, how many dwarf planets exist, and how each one was found — you’ll get the observing details that matter at the eyepiece and the camera: the apparent magnitude of each object, the minimum aperture you need, the best time to catch it near opposition, and how to confirm a faint point of light by tracking its motion across two nights. Some, like Ceres, sit within reach of ordinary binoculars; others, like Eris, demand a 25-inch (or larger) telescope and a dark sky. Wherever it helps, I’ll share first-hand notes from chasing these targets myself.

Table of contents

1. What is a dwarf planet?
2. Dwarf planet vs planet vs asteroid
3. How many dwarf planets are there?
4. The 5 official dwarf planets
5. How dwarf planets compare in size
6. Is Pluto a dwarf planet?
7. Dwarf planet candidates
8. Dwarf planets in order from the Sun
9. How to observe and photograph dwarf planets
10. Frequently asked questions

What is a dwarf planet?

A dwarf planet is a round object that orbits the Sun but has not cleared its orbital neighborhood of other bodies, and it is not a moon. That single sentence captures the whole idea, but the official definition is worth unpacking because it is exactly where dwarf planets split off from the eight major planets.

The rules come from the International Astronomical Union (IAU), which created the category in 2006. Under that resolution, a body must pass three tests to be a full-fledged planet:

1. It orbits the Sun — not another planet (that would make it a moon).
2. It is massive enough to be round. Its own gravity pulls it into a near-spherical shape, a state astronomers call hydrostatic equilibrium.
3. It has “cleared its neighborhood.” Over billions of years it has become gravitationally dominant, sweeping up, flinging away, or capturing the smaller debris that shares its orbit.

A dwarf planet checks boxes 1 and 2 but fails box 3. It circles the Sun and it is round, yet it still shares its lane with a crowd of comparably sized icy or rocky bodies it was never massive enough to push aside. The IAU added one more condition that quietly does a lot of work: a dwarf planet must not be a satellite. That is why our own Moon does not count — it is round, but it orbits Earth rather than the Sun directly, which makes it a satellite, not a dwarf planet.

What does “cleared the neighborhood” actually mean? Think of a planet as a snowplow on a highway. A full planet has plowed its lane clean, so it cruises along essentially alone except for its own moons. A dwarf planet is more like a car stuck in stop-and-go traffic — it stays in its lane, but it is hemmed in by thousands of other vehicles it can never clear. Pluto, for example, is just one of countless icy worlds in the Kuiper Belt; Ceres is one body among many in the asteroid belt. Neither dominates its zone, so neither makes the planet cut.

It is also worth knowing the scale: every dwarf planet is smaller than Earth’s Moon — even the largest, Pluto and Eris, are only about two-thirds the Moon’s diameter — which is one reason the count and the boundaries still spark debate. We dig into the full planet-versus-dwarf-planet contrast in the next section, and the famous test case — Pluto, reclassified under exactly these rules — gets its own deep dive on the dedicated Pluto dwarf planet guide. For how all of this fits the bigger picture, the planets of the solar system page covers the eight worlds that did clear their orbits.

Dwarf planet vs planet vs asteroid

A dwarf planet sits in the middle of three categories the International Astronomical Union uses to sort objects orbiting the Sun. The fastest way to tell them apart is to ask three yes-or-no questions: Is it round? Does it orbit the Sun? Has it cleared its orbital neighborhood?

The single line that separates a planet from a dwarf planet is the third one: a planet has swept its orbital path clean, pulling in or flinging away nearly everything else of comparable size, while a dwarf planet shares its lane with countless similar objects. Pluto, for example, is just one of thousands of icy bodies in the Kuiper Belt, so it fails that test even though it is clearly round.

The line between a dwarf planet and an asteroid is different: it comes down to shape. Asteroids and other small bodies are not massive enough for their own gravity to crush them into a sphere, so they stay irregular, like cosmic potatoes. Ceres is the classic borderline case — it is the largest object in the asteroid belt, but because it is big enough (about 940 km / 584 mi across) to pull itself round, the IAU promoted it to dwarf planet in 2006. It still lives among the asteroids, which is why people often call it both: Ceres is physically located in the asteroid belt, but its category is “dwarf planet,” not “asteroid.” In practical terms, every planet is far larger than every dwarf planet, and every dwarf planet is round while nearly every asteroid is not. Note that none of these three categories includes moons: a body has to orbit the Sun directly, not another planet, to qualify at all. For how each of these worlds fits into the bigger picture, see the solar system overview.

How many dwarf planets are there?

The short answer: five. The International Astronomical Union (IAU) officially recognizes exactly five dwarf planets — Ceres, Pluto, Haumea, Makemake, and Eris. That number has not changed since 2008, when Makemake and Haumea were added to the list (Ceres, Pluto, and Eris came first, in 2006).

But the honest answer is “five officially, with many more waiting in line.” The real count is genuinely fuzzy, and here is why.

Why the number is so hard to pin down

The sticking point is the second IAU rule: to be a dwarf planet, an object must be massive enough that its own gravity pulls it into a round shape (a state called hydrostatic equilibrium). Confirming roundness sounds simple, but most candidates orbit far out in the Kuiper Belt and the trans-Neptunian region, tens to hundreds of times farther from the Sun than Earth. From that distance they appear as little more than dim points of light, even through the world’s largest telescopes. We often cannot measure their exact size, shape, or mass well enough to say for certain.

So the IAU stays conservative and only confirms an object once the evidence is solid. Astronomers, meanwhile, keep a longer working list of bodies they are confident will qualify — Mike Brown’s catalog alone flags dozens of “highly likely” and hundreds of “possible” dwarf planets across its likelihood tiers. New discoveries — like the distant candidate 2017 OF201, announced in May 2025 — keep stretching that list. Every wide-field survey of the outer solar system turns up more icy worlds, which is why “5” is the rule-book answer but almost certainly not the final one.

For the full rundown, see the comparison table of all five official dwarf planets below, then explore the candidate dwarf planets still awaiting recognition.

The 5 official dwarf planets

The International Astronomical Union (IAU) recognizes five dwarf planets. Listed in order of their average distance from the Sun, they are Ceres, Pluto, Haumea, Makemake, and Eris. Only Ceres orbits inside the asteroid belt; the other four are frozen worlds far beyond Neptune in the Kuiper Belt and scattered disk. Every one of them is smaller than Earth’s Moon (about 3,475 km / 2,159 mi across), which tells you just how compact these little worlds really are.

Ceres is the odd one out. It sits in the asteroid belt between Mars and Jupiter, making it the only dwarf planet you can reach without crossing Neptune’s orbit. At about 940 km (584 mi) wide, it holds roughly a third of the entire asteroid belt’s mass. NASA’s Dawn spacecraft orbited Ceres from 2015 to 2018 and found bright salt deposits in Occator Crater, along with strong evidence of briny water and a possible muddy subsurface ocean. Ceres is also the easiest dwarf planet to observe, brightening to roughly magnitude 7 at a favorable opposition, so it shows up in ordinary binoculars.

Pluto is the most famous of the five and the largest by diameter, at about 2,377 km (1,477 mi). When NASA’s New Horizons probe flew past in July 2015, it revealed a stunning, geologically active world with a vast heart-shaped plain of frozen nitrogen ice. Pluto also commands a system of five moons, dominated by Charon, which is so large (about half Pluto’s diameter, roughly 1,212 km / 753 mi) that the two bodies orbit a point in empty space between them. Pluto carries far too much story for this hub page, so we cover its reclassification debate, the New Horizons flyby, and its observing details in depth on the dedicated Pluto dwarf planet guide.

Haumea is the strangest body on this list. It spins so fast, completing one rotation in just 3.9 hours, that its own rotation has stretched it into an egg shape: its longest axis runs roughly 2,100 km (about 1,300 mi), nearly twice the length of its shortest (polar) axis, even though its volume-equivalent mean diameter is only about 1,560 km (970 mi). That rapid spin probably came from an ancient collision, which also produced its two moons, Hiʻiaka and Namaka, and a family of icy fragments scattered nearby. In 2017, astronomers watching Haumea pass in front of a distant star discovered a thin ring around it, about 70 km (40 mi) wide. This was the first ring ever found around a trans-Neptunian object, and the ring particles loop around the planet once for every three times Haumea spins.

Makemake is the second-brightest known object in the Kuiper Belt and trans-Neptunian region after Pluto. About 1,430 km (888 mi) across, it has a reddish surface so reflective and cold that frozen methane and ethane likely coat it like a crust. For years Makemake appeared to be solitary, but it turned out to have a small, dark moon nicknamed MK 2 — roughly 175 km (110 mi) wide — first imaged by the Hubble Space Telescope in 2015 and announced in 2016. The moon’s faintness against its bright parent is exactly why it stayed hidden for so long.

Eris is the heavyweight that changed everything. Although Pluto edges it out in diameter, Eris (about 2,326 km / 1,445 mi) is roughly 27% more massive, making it the most massive dwarf planet of all. Its discovery in 2005 forced astronomers to ask a hard question: if Pluto counts as a planet, why not this slightly heavier twin sitting even farther out in the scattered disk? That debate led directly to the IAU’s 2006 vote and the modern definition of a dwarf planet. Eris has one known moon, Dysnomia, and orbits so far away (around 68 AU on average) that it remains a faint point of light even in large telescopes.

How dwarf planets compare in size

Numbers in a table are one thing; seeing the scale is another. Every dwarf planet is smaller than Earth’s Moon, and most science pages never show you that side by side. Here is how the five official dwarf planets stack up against the Moon and Earth, drawn to scale by diameter.

A few things jump out once you see it laid out. Earth dwarfs the whole group — you could line up more than five Plutos across one Earth. The Moon, which we never think of as small, is bigger than every dwarf planet by a clear margin. And the five dwarf planets themselves split into two tiers: Pluto and Eris are near twins at roughly 2,300–2,400 km, while Ceres is so much smaller (just 940 km) that it would fit inside Pluto with room to spare. That huge spread in size is part of why the category feels so loose, and why the boundary with both planets and asteroids keeps generating debate. Mass tells a slightly different story than diameter, too: Eris is narrower than Pluto but about 27% heavier, because it is denser and packs more rock beneath its ice.

Is Pluto a dwarf planet?

Yes, Pluto is a dwarf planet. The IAU reclassified it from the ninth planet to a dwarf planet in 2006, and it has held that status ever since. It passes the first two planet tests easily — it orbits the Sun and it is round — but it fails the third. Pluto orbits inside the crowded Kuiper Belt, sharing its lane with countless icy bodies and even crossing Neptune’s path, so it has never cleared its neighborhood. That single missed criterion is why it is a dwarf planet rather than a planet.

The trigger was the 2005 discovery of Eris, a world about the same size as Pluto and, as we now know, slightly more massive. If Pluto counted as a planet, Eris had to as well — and many more Pluto-sized bodies were likely waiting in the outer Solar System. Rather than keep adding planets, the IAU wrote a formal definition of “planet” for the first time, and Pluto landed in the new dwarf-planet category. The full story — the five moons, the 2015 New Horizons flyby, the famous nitrogen “heart,” the lingering “geophysical definition” debate, and whether Pluto could ever be a planet again — lives on our in-depth Pluto dwarf planet guide. You can also see where Pluto fits among the icy worlds of the Kuiper Belt and trans-Neptunian objects.

Dwarf planet candidates

Beyond the five worlds the IAU officially recognizes, astronomers have found dozens of bodies in the outer solar system that almost certainly qualify as dwarf planets. They are round (or nearly so) and orbit the Sun far past Neptune, but the IAU has not formally added them to the list. The reason is almost always the same: they are so distant and so faint that confirming they are massive enough to have pulled themselves into a round shape (hydrostatic equilibrium) is extremely hard. Until that roundness is nailed down, they stay “candidates.”

The strongest candidates live in the Kuiper Belt and scattered disk, the icy reservoir of trans-Neptunian objects beyond Neptune’s orbit.

Each of these is large enough that most astronomers treat it as a dwarf planet in practice. Mike Brown, who co-discovered several of them, keeps a running tally that lists dozens of “highly likely” and hundreds of “possible” dwarf planets across the outer solar system. The catalog keeps growing, too: in May 2025, astronomers announced 2017 OF201, a candidate (~700 km across) on an extreme ~25,000-year orbit with a semi-major axis near 840 AU that swings out to roughly 1,600 AU at its farthest, hinting at many more frozen worlds still waiting in the dark.

There is fresh science here as well. In 2024, a long campaign of stellar occultations (datasets gathered from 2011 through 2024) refined Quaoar’s dimensions to roughly 1,167 × 1,111 × 1,020 km and supported a striking idea: Quaoar’s slightly squashed, elongated figure appears to be a “frozen-in” shape. The thinking is that Quaoar was once spinning faster and bulged out under that spin, then its rotation slowed — likely from tidal interaction with its moon Weywot — and the rigid, icy body locked in the old shape instead of relaxing into a perfect sphere. That makes its compliance with hydrostatic equilibrium genuinely ambiguous, which is part of why the IAU has not rushed to promote it.

Spectroscopy is moving fast, too. The James Webb Space Telescope (JWST) has begun taking detailed infrared spectra of trans-Neptunian objects, sorting them into surface-composition families and detecting ices like carbon dioxide, water, and complex carbon-bearing compounds on the faint, far-off candidates that ground telescopes can barely register. Those measurements are exactly the kind of evidence that will eventually push some of today’s candidates onto the official list — and they make the outer Solar System feel less like a blank map every year.

Dwarf planets in order from the Sun

The five IAU-recognized dwarf planets are spread across two very different regions. Ceres orbits close in, within the asteroid belt between Mars and Jupiter. The other four are far out in the cold trans-Neptunian region, beyond the planet Neptune. Distances out there are vast: one astronomical unit (AU) equals the Earth-Sun distance of about 150 million km (93 million mi), so Eris at roughly 68 AU sits more than 10 billion km (6.3 billion mi) from the Sun.

Here are the five official dwarf planets, ordered by their average distance from the Sun:

A few notes on the ordering. These are average distances, and because dwarf-planet orbits are highly elliptical, the real positions overlap and shift over time. Pluto’s orbit, for example, sometimes brings it closer to the Sun than Neptune. Eris swings even farther on its long path, reaching nearly 98 AU at its most distant point.

The likely dwarf planet Sedna sits in a class of its own, far beyond Eris. Its average distance is around 500 AU, and its extreme orbit carries it out past 900 AU at aphelion, taking roughly 11,000 years to circle the Sun once. Objects like Sedna and the 2017 OF201 candidate hint at how much of the outer Solar System we have yet to map.

How to observe and photograph dwarf planets

Here is the honest truth most science pages skip: with the exception of Ceres, dwarf planets are hard targets. None of them shows a disk in an amateur telescope. They appear as faint, star-like points, and the only way you confirm you’ve actually caught one is by photographing the same field on two or three nights and watching your point of light shift against the fixed background stars. That slow crawl is the proof. You are not resolving a world; you are detecting motion.

Observing difficulty, easiest to hardest:

Ceres is genuinely fun and accessible: around magnitude 7 at opposition, it is brighter than Neptune and easily reaches binoculars or a small scope even under suburban light pollution. Sweep the right star field, note the one “star” that isn’t on your chart, and come back the next clear night. Pluto is the classic rite of passage. At magnitude 14-plus it demands a 10-inch or larger scope, a transparent sky, and patience to match it against the background over several nights. Haumea, Makemake, and Eris belong to deep-imaging specialists with large apertures and stacked exposures.

The candidates raise the bar even higher. Quaoar and Eris both sit near magnitude 18.7–18.9, faint enough that you really want a 25–30-inch (or larger) instrument and clean stacking to pull them out of the noise. Orcus is similar at around magnitude 19. Gonggong (~21.5) and Sedna (~20.5–21) are effectively beyond visual reach for amateurs — they are observatory-class targets, recorded only in long exposures by large telescopes. If you set out to image a candidate, treat it exactly like the faint official ones: plan around opposition, shoot multiple nights, and let the object’s motion confirm the catch.

This is where I can speak from experience. I’ve imaged from a remote 12.5-inch Alluna Ritchey-Chrétien with an SBIG STL-11000 at Deepsky Chile, and even with that aperture under Bortle 1 skies, Ceres and Pluto never showed as discs — at the rig’s plate scale they landed as a single faint 1–2 pixel dot, indistinguishable from the field stars on any one frame. The way I confirmed each one was the old-fashioned way: shoot the same field on two separate nights, register the frames on the background stars, then blink the two stacks back and forth. The one “star” that has hopped a few pixels between sessions is your target. That little jump is the entire payoff — not a picture of a world, but proof you tracked a body billions of kilometers away across the sky. It is a quiet, slow thrill, and it never gets old. (More about the rig and how I work on the about page.)

A few StellarNomads tools make the planning much easier:

• Use the FOV simulator to frame Ceres near opposition for your exact scope and camera, so you know which star field to shoot and can spot the interloper fast when you blink your two nights together.
• Run the sub-exposure calculator to plan exposure length for the magnitude-17-plus targets like Makemake and Haumea, swamping read noise without blowing out nearby stars.
• The all-in-one astrophotography calculator dials in your image scale and sampling for the faint, point-source TNOs, so a candidate like Quaoar lands cleanly across your subs.

Plan around opposition, when each object sits highest and brightest, check a current ephemeris for its precise position, and let movement be your confirmation.

Frequently asked questions

What is a dwarf planet?
A dwarf planet is a round body that orbits the Sun but has not cleared its orbital neighborhood of other debris, and is not a moon of another planet. It meets two of the three criteria for full planethood but fails the third, which is why it sits in its own category.

How many dwarf planets are there?
There are 5 officially recognized by the International Astronomical Union (IAU): Ceres, Pluto, Haumea, Makemake, and Eris. Many astronomers commonly accept about 9 (adding Quaoar, Sedna, Gonggong, and Orcus), and NASA notes there may be 100 or more dwarf planets in the solar system, with some estimates running into the hundreds as we survey the outer regions.

Is Pluto a dwarf planet?
Yes. Pluto was reclassified from the ninth planet to a dwarf planet in 2006 because it shares its region of the Kuiper Belt with countless other icy bodies and has not cleared its orbit. We cover the full reclassification story on the dedicated Pluto guide.

Will Pluto ever be a planet again?
Probably not under the current rules — Pluto still shares its lane in the Kuiper Belt, so it still fails the “cleared its neighborhood” test. The official answer could only change if the IAU adopted a different definition, and some scientists do push for a “geophysical” definition (round equals planet) that would restore it. For now, though, Pluto remains a dwarf planet. The full case for and against lives on our Pluto guide.

Is the Moon a dwarf planet?
No. Our Moon is round and large, but it orbits Earth rather than the Sun directly, which makes it a natural satellite, not a dwarf planet. To qualify as any kind of planet — full or dwarf — a body has to orbit the Sun on its own, not circle another world.

What are the 5 dwarf planets?
In order from the Sun, they are Ceres (in the asteroid belt), then Pluto, Haumea, Makemake, and Eris (all in the Kuiper Belt and trans-Neptunian region).

What is the largest dwarf planet?
It depends on how you measure. Pluto is the largest by diameter at about 2,377 km (1,477 mi), while Eris is the most massive, packing roughly 27% more mass into a slightly smaller ball about 2,326 km (1,445 mi) across. Eris’s higher density is why it tips the scales despite being narrower.

What is the smallest dwarf planet?
Among the 5 official dwarf planets, Ceres is the smallest at roughly 940 km (584 mi) across. It is also the only one in the asteroid belt rather than the outer solar system.

Is Ceres a dwarf planet, an asteroid, or both?
Its category is “dwarf planet.” Ceres was the first object ever called an asteroid (in 1801), and it still physically lives in the asteroid belt, which is why people often describe it as both. But in 2006 the IAU reclassified it as a dwarf planet because it is large enough to be rounded by its own gravity — something true asteroids are not. So it is a dwarf planet that happens to orbit among the asteroids, and the only one in the inner solar system.

What is the difference between a dwarf planet and a planet?
Both orbit the Sun and are massive enough to be round. The difference is that a true planet has cleared its orbital path of other bodies, while a dwarf planet has not. Every dwarf planet is also smaller than Earth’s Moon.

Can you see dwarf planets with a telescope?
Some, yes. Ceres reaches magnitude 7 to 9 near opposition and is visible in binoculars or a small telescope, while Pluto (mag ~14.4) needs a 10-12 inch scope. Haumea, Makemake, and Eris (mag 17 to 19) require 16-30 inch apertures, and you confirm them by their slow drift against the stars over a night or two. Use our FOV simulator and sub-exposure calculator to plan these faint targets.

Will there be more dwarf planets?
Almost certainly. Candidates like Sedna, Quaoar, Gonggong, and Orcus already await confirmation, and the May 2025 discovery of 2017 OF201 on a roughly 840-AU orbit shows how many remain hidden. Most are simply too far and too dim for us to confirm their roundness yet, so the official count will keep growing as telescopes — and instruments like JWST — improve.

About the author: Hamza has been an astrophotographer since 2008, capturing the deep sky from a remote rig at Deepsky Chile — a 12.5-inch Alluna Ritchey-Chrétien on a Paramount MX+ with an SBIG STL-11000 CCD, under the Bortle 1 skies of the Chilean Andes. He has chased faint solar-system targets like Ceres and Pluto across multiple nights to confirm their motion firsthand. Follow his work on Instagram @stellar.nomads.

Ready to hunt a dwarf planet yourself? Start with the FOV simulator to frame Ceres near opposition, plan your faint-target exposures with the sub-exposure calculator, and dial in sampling for the distant TNOs using the all-in-one astrophotography calculator. Then work your way back up to the Solar System hub to explore the planets, asteroids, and the Kuiper Belt.

By Hamza — astrophotographer since 2008, imaging from a remote rig (Alluna 12.5″ Ritchey-Chrétien, Paramount MX+, SBIG STL-11000) at Deepsky Chile.

Quick answer: The solar system is the Sun and everything bound to it by gravity — 8 planets, 5 officially recognized dwarf planets, more than 400 planetary moons (890+ counting moons of dwarf planets, asteroids and TNOs), more than 1.4 million tracked asteroids, and about 4,600 known comets. It formed 4.6 billion years ago, and the Sun holds 99.86% of all its mass.

The solar system is our cosmic neighborhood: one ordinary star and the vast swarm of worlds, rocks, ice, and dust held captive by its gravity. It stretches from the scorched rock of Mercury, closest to the Sun, out past Neptune to the frozen Kuiper Belt and the distant Oort Cloud — a shell of comets so far away that the Sun looks like just another star. Everything you can see with the naked eye on a clear night, plus billions of objects you cannot, belongs to this single gravitational family that took shape 4.6 billion years ago from a collapsing cloud of gas and dust.

A quick note on those counts, because they grow every month. Of the 1.4-million-plus minor planets astronomers have tracked, roughly 895,000 are formally numbered, and the rest await enough observations to lock down their orbits. The five dwarf planets — Ceres, Pluto, Haumea, Makemake, and Eris — are the only ones the International Astronomical Union has officially blessed, though dozens more candidates are waiting in the wings. Moon counts have exploded too, especially around Saturn and Jupiter, as deep surveys reveal tiny new satellites.

This guide is different from the generic science pages. It is a complete pillar covering the Sun, all eight planets, the dwarf planets, and the small bodies — asteroids, comets, and trans-Neptunian objects — alongside something the encyclopedias leave out: how to actually see and photograph each of these worlds from your own backyard. For every object class below you will find an observing-difficulty note — naked-eye, binocular, telescope, or imaging-only — drawn from real nights under the sky, including my own from the southern hemisphere. Think of this page as the hub: each section gives you the essentials, then links down to a deep-dive when you want to go further.

Table of contents

1. What is the solar system?
2. How the solar system formed
3. The solar system in the Milky Way
4. Objects in the solar system: the master comparison table
5. The Sun: our star
6. The eight planets
7. Dwarf planets
8. Small solar system bodies: asteroids, comets, Centaurs and TNOs
9. Asteroids
10. Comets
11. Trans-Neptunian objects: the Kuiper Belt & Oort Cloud
12. Is there a Planet Nine?
13. Moons
14. Meteors and meteor showers
15. Where does the solar system end?
16. The state of solar-system exploration (2026)
17. How to observe and photograph the solar system
18. Best targets for beginners
19. Solar system records and fun facts
20. Frequently asked questions

What is the solar system?

The solar system is the Sun and everything held in orbit around it by gravity. That includes the eight planets in order from the Sun, five recognized dwarf planets, more than 400 planetary moons (890+ counting moons of dwarf planets, asteroids and TNOs), and millions of smaller bodies like asteroids, comets, and distant trans-Neptunian objects.

At the center sits one star. The Sun is so dominant that nothing else comes close to rivaling it.

The Sun runs everything

The Sun holds about 99.86% of all the mass in the solar system. Jupiter and Saturn make up most of the leftover sliver, and every other planet, moon, and rock shares the tiny remainder.

That overwhelming mass is why the Sun governs the orbits. Gravity scales with mass, so the Sun’s pull sets the path of every planet and comet, even ones that take thousands of years to loop around it. The whole system is, quite literally, a collection of objects falling endlessly around a single star.

Measuring the distances: the astronomical unit

Distances out here are too large for kilometers to feel meaningful, so astronomers use the astronomical unit (AU). One AU is the average distance from Earth to the Sun, about 150 million km (93 million miles).

A clearer way to picture an AU is by light-travel time. Sunlight takes roughly 8 minutes and 20 seconds to reach Earth, so 1 AU is “8 light-minutes” away. Use that ruler and the scale of the system snaps into focus:

The light that lets you see Jupiter through a telescope left the Sun nearly an hour ago. When you observe the outer planets, you are always looking slightly into the past.

Why the solar system is flat

The planets do not orbit at random angles. They travel in nearly the same plane, like marbles rolling on a tabletop. That plane is called the ecliptic.

This flatness is a fingerprint of how the system formed. It condensed from a spinning cloud of gas and dust that flattened into a disk, and the planets grew from that disk, inheriting its plane.

For observers, the ecliptic is the single most useful line in the sky. The Sun, Moon, and every planet ride along it, tracing the same arc the Sun follows by day. So if you want to find Mars, Jupiter, or Saturn at night, you scan that band, not the whole sky. From my own imaging runs at Deepsky Chile, planning a session always starts with where the ecliptic sits, because that is where the planets and the Moon will be.

How the solar system formed

The solar system formed about 4.6 billion years ago when a giant cloud of gas and dust collapsed under its own gravity, flattened into a spinning disk, and built the Sun and planets from the leftovers. This is the nebular hypothesis, and it remains the best-supported model of our origins.

It starts with a molecular cloud — a cold, dark stretch of mostly hydrogen and helium seeded with heavier elements from earlier dead stars. A nearby shockwave, perhaps from an exploding star, nudged part of this cloud into collapse. As the material fell inward, it spun faster and flattened into a protoplanetary disk, much like pizza dough stretched by a spinning cook.

Most of the matter piled into the dense, hot center. When that core grew massive and hot enough, nuclear fusion ignited and the Sun switched on — claiming over 99.8% of the system’s mass. The young Sun’s heat and wind then carved the rest of the disk into the layout we see today.

That layout was set by the frost line (also called the snow line), the distance from the Sun — roughly 2.7 astronomical units, out in today’s asteroid belt — beyond which it was cold enough for water, ammonia, and methane to freeze into ice:

• Inside the frost line only metals and rock could stay solid, so the inner zone built small, dense, rocky worlds — Mercury, Venus, Earth, and Mars. Explore each of them in the planets of the solar system sub-hub.
• Beyond the frost line ice was abundant, so growing cores swept up huge amounts of solid material plus gas, becoming the giants — Jupiter, Saturn, Uranus, and Neptune.

Planets grew by accretion: dust grains stuck together into pebbles, pebbles into boulders, and boulders into planet-sized bodies called planetesimals that swept their orbits clean.

The leftovers never finished. Rubble that Jupiter’s gravity kept from forming a planet became the asteroid belt, while icy crumbs in the cold outer reaches became the comets and the distant worlds of the Kuiper Belt and beyond.

How do we know the age? We date it from the oldest meteorites — primitive chunks of that original disk that fell to Earth. Radiometric dating of these “calcium-aluminium-rich inclusions” gives a remarkably consistent 4.567 billion years, pinning the moment our solar system began. For more on the collapsing-cloud model, see NASA’s overview of how the solar system formed.

The solar system in the Milky Way

The solar system is not floating in empty space — it rides inside a much larger structure, the Milky Way galaxy, and it is constantly on the move. Knowing where our neighborhood sits in the galaxy puts every distance on this page into a humbling new perspective.

We live in a quiet suburb of the galaxy called the Orion Arm (also known as the Orion Spur or Local Arm), a minor spiral feature between two of the galaxy’s major arms, the Sagittarius Arm and the Perseus Arm. It is a good address for life: far from the crowded, radiation-soaked galactic core, in a calm stretch of the disk.

The Sun and its whole family of planets sit roughly 26,000 light-years from the center of the Milky Way, a little more than halfway out from the core to the visible edge of the galactic disk. The center itself hosts a supermassive black hole, Sagittarius A*, about four million times the mass of the Sun.

And we are not standing still. The entire solar system orbits the galactic center at a staggering roughly 828,000 km/h (about 514,000 mph). Even at that blistering speed, the galaxy is so enormous that one full lap — known as a galactic year — takes about 230 million years. The last time the Sun was in its current galactic position, dinosaurs had not yet appeared on Earth.

For an observer, the Milky Way is the faint, glowing band that arches across a truly dark sky. When you look toward the densest part of that band — in the direction of the constellation Sagittarius — you are looking straight toward the galactic core, through tens of thousands of light-years of stars, gas, and dust. From my dark-sky site in Chile, that core region rides high overhead in the southern winter, and it is one of the great rewards of imaging from the southern hemisphere.

Objects in the solar system: the master comparison table

The solar system is arranged in a clear sequence outward from the Sun. The four small, rocky inner planets come first, then the asteroid belt, then the four giant outer planets, and finally a vast frontier of icy bodies that stretches almost a quarter of the way to the nearest star.

Here is the order from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. The asteroid belt sits between Mars and Jupiter, marking the boundary between the inner and outer solar system.

The table below is the single master reference for this whole guide. It gathers every major object class — the Sun, the eight planets, the five dwarf planets, and the small-body regions — into one place, with distance, size, orbital period, day length, moon count, temperature, and how hard each is to observe from the ground.

A quick way to memorize the eight planets in order is the classic mnemonic: My Very Educated Mother Just Served Us Nachos — the first letter of each word matches a planet (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune). Older versions ended in “Nine Pizzas” for Pluto, but Pluto’s 2006 reclassification as a dwarf planet dropped it from the list.

One AU (astronomical unit) equals the average Earth–Sun distance, about 150 million km (93 million miles), so the scale jumps fast: Neptune orbits 30 times farther from the Sun than Earth does, and the Oort Cloud may reach 100,000 AU. For a deeper look at each world, including observing tips and the best times to view them, see our complete guide to the planets.

The Sun: our star

The Sun is the star at the heart of our solar system, and everything else orbits it. It is a G2V yellow dwarf, a middle-aged, middle-sized star roughly 4.6 billion years old. Despite “dwarf” in the name, it is enormous: about 1.39 million km (865,000 mi) across, wide enough to line up 109 Earths edge to edge.

Its gravity is the glue that holds the whole neighborhood together. The Sun packs roughly 99.86% of all the mass in the solar system, leaving every planet, moon, asteroid, and comet to share the last fraction of a percent. Learn more about its structure and life cycle on our dedicated guide to the Sun.

Powered by fusion. Deep in the core, where temperatures top 15 million °C (27 million °F), hydrogen fuses into helium. The Sun converts about 600 million tonnes of hydrogen every second, turning roughly 4 million tonnes of that into pure energy. That energy takes tens of thousands of years to claw its way to the surface, then just 8 minutes and 20 seconds to cross 150 million km (93 million mi) and reach your eyes.

A layered, restless star. The visible “surface” is the photosphere, a churning layer at about 5,500 °C (9,900 °F). Above it lies the corona, the faint outer atmosphere that paradoxically blazes to 1–3 million °C (1.8–5.4 million °F) and only becomes visible to the naked eye during a total solar eclipse. The photosphere is freckled with sunspots, cooler magnetic regions (around 3,500–4,000 °C / 6,300–7,200 °F) that come and go on an 11-year activity cycle. When the Sun’s twisted magnetic field snaps, it unleashes solar flares and coronal mass ejections, hurling charged particles outward. Those particles spark the auroras (northern and southern lights) when they slam into Earth’s magnetic field.

The only star you can image in surface detail. Every other star is a single point of light, even in the largest telescopes. The Sun is the lone exception: from your own backyard you can resolve sunspots, granulation, and, with the right gear, flaming prominences arcing off the edge. It is the most rewarding target in all of astrophotography for sheer detail.

SAFETY — read this first. NEVER look at the Sun through any telescope, binoculars, or camera without a purpose-made solar filter, and NEVER point unfiltered optics at it. Focused sunlight will cause instant, permanent blindness and can melt your equipment in seconds. Use only a certified full-aperture white-light solar filter (fitted over the front of the scope) or a dedicated hydrogen-alpha solar telescope. “Solar eclipse glasses” are for naked-eye use only, NOT for use with optics. When in doubt, do not look.

Observing difficulty: naked-eye with a certified solar filter only; binoculars or a telescope only with a full-aperture white-light filter or a dedicated hydrogen-alpha scope. A white-light filter reveals sunspots and the granular photosphere, while a hydrogen-alpha scope adds prominences and surface filaments. Best time: any clear day, with steadiest air usually in the morning. Minimum aperture: any size works — even a 60 mm scope shows sunspots safely with the right filter. The Sun is the one deep-space target that is best in broad daylight, making it perfect for observers who can’t stay up late.

The eight planets

Eight planets orbit the Sun. In order from the Sun, they are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Each one is a world unto itself, and several are bright, rewarding targets for backyard telescopes.

So what officially counts as a planet? In 2006, the International Astronomical Union (IAU) settled the question with a three-part test. To be a planet, a body must:

1. Orbit the Sun — not another planet (which would make it a moon).
2. Be massive enough to be round — its own gravity pulls it into a near-spherical shape (a state called hydrostatic equilibrium).
3. Have cleared its orbital neighborhood — it gravitationally dominates its lane around the Sun, sweeping up or flinging away other debris.

That third rule is the one that demoted Pluto. Pluto is round and orbits the Sun, but it shares its zone with countless icy bodies in the Kuiper Belt, so it became a dwarf planet instead. For the full roster and the science of these worlds, see the dedicated guide to the planets.

Two planet families

The eight planets split cleanly into two groups, separated by the asteroid belt.

• Terrestrial (rocky) planets — Mercury, Venus, Earth, and Mars. Small, dense, rocky worlds with solid surfaces you could (in principle) stand on. These are the four inner planets.
• Giant planets — Jupiter, Saturn, Uranus, and Neptune. Huge, low-density worlds with no solid surface. Astronomers split these further into gas giants (Jupiter and Saturn, dominated by hydrogen and helium) and ice giants (Uranus and Neptune, richer in water, ammonia, and methane “ices”). These are the four outer planets.

A quick tour, world by world

Mercury — the smallest and fastest planet, racing around the Sun every 88 days. It has almost no atmosphere (just a thin exosphere), so its surface swings from about 430 °C (800 °F) in daylight to −180 °C (−290 °F) at night — the widest temperature range of any planet. From a backyard, it never strays far from the Sun, so catch it low in twilight during a “greatest elongation.” Read more about observing the innermost planet, Mercury.

Venus — Earth’s near-twin in size, but a hellish one. A thick carbon-dioxide atmosphere traps heat in a runaway greenhouse effect, baking the surface to about 465 °C (870 °F), hot enough to melt lead. Venus is the brightest planet in our sky and, through a telescope, shows phases like the Moon.

Earth — the only world known to harbor life, and the only one with liquid water oceans on its surface. Its large Moon stabilizes the planet’s tilt — holding our obliquity within a narrow band near 23.4° — which helps keep our climate steady over geological time.

Mars — the rusty “Red Planet,” colored by iron oxide in its soil. It hosts the tallest volcano in the solar system, Olympus Mons, which rises about 22 km (14 mi) above the surrounding plains — roughly two and a half times the height of Mount Everest. Mars is a classic telescope target near opposition, when its polar caps and dark surface markings sharpen into view. Get the full picture in our Mars observing guide.

Jupiter — the king of the planets, more massive than all the others combined (about 2.5 times over). Its Great Red Spot is a storm still wider than Earth that has been tracked through telescopes for nearly two centuries of continuous observation, though it has been steadily shrinking and is now the smallest ever measured. Even a small telescope reveals its cloud bands and the four bright Galilean moons, which shift position from night to night — explore them in our Jupiter guide.

Saturn — the jewel of the solar system, famous for its dazzling ring system made of countless chunks of ice and rock. It’s the least dense planet — so low in density it would float in water if you had a big enough bathtub. It also reigns as the solar system’s moon king, with hundreds of confirmed satellites. The moment those rings snap into focus in an eyepiece is unforgettable; see how in our Saturn guide.

Uranus — the tipped-over ice giant, rotating on its side at a 98° tilt, likely from an ancient giant impact. This means each pole gets about 42 years of continuous sunlight followed by 42 years of darkness. It glows a pale blue-green and appears as a tiny disk in a backyard telescope.

Neptune — the most distant planet, a deep-blue ice giant about 30 times farther from the Sun than Earth. It boasts the fastest winds in the solar system, exceeding 2,000 km/h (1,200 mph). Far too faint for the naked eye, Neptune was the first planet found by mathematical prediction rather than direct observation, in 1846.

Observing difficulty for the eight planets: naked-eye for Mercury, Venus, Mars, Jupiter, and Saturn at the right time of year; binoculars or a small telescope for Uranus (a faint blue-green star at magnitude 5.7); telescope or imaging only for Neptune (magnitude 7.8, never naked-eye). Best time for the outer planets is opposition; Mercury and Venus show best near greatest elongation. Minimum aperture for ring and cloud-band detail is about 60–80 mm.

Moon tallies climb almost every year as deep surveys keep catching faint outer satellites, so the giant-planet counts above reflect the latest 2026 figures. Together, these eight worlds span the full range of planetary possibilities, from scorched rock to frozen gas, and four of them — Mars, Jupiter, Saturn, and Venus — are within easy reach of a modest telescope on any clear night.

Dwarf planets

A dwarf planet is a body that orbits the Sun and is massive enough for its own gravity to pull it into a round (or nearly round) shape, but that has not cleared the neighborhood around its orbit of other debris. That last point is the key difference from a true planet. A dwarf planet shares its orbital zone with asteroids, Kuiper Belt objects, or other rubble it was never big enough to sweep up.

This definition came from the International Astronomical Union (IAU) in August 2006. The same vote famously demoted Pluto from the ninth planet to a dwarf planet, shrinking the official planet count from nine to eight. It remains one of the most debated decisions in modern astronomy, and our deep dive on Pluto’s reclassification and what we lost unpacks the science and the controversy.

The IAU currently recognizes five dwarf planets:

Four of the five live in the cold outer solar system beyond Neptune, in the Kuiper Belt and scattered disc. Only Ceres sits closer in, tucked inside the asteroid belt between Mars and Jupiter.

Expect this list to grow. Astronomers estimate that dozens, possibly hundreds, of dwarf planets are still waiting in the outer solar system. Strong candidates such as Gonggong, Quaoar, Sedna, and Orcus already meet the size and shape requirements; the IAU simply has not formally classified them yet. For the full roster of candidates, observing notes, and how these icy worlds connect to the broader population of trans-Neptunian objects beyond Neptune’s orbit, see our complete guide to the solar system’s dwarf planets.

Observing difficulty: imaging-only for nearly all of them. Pluto is the brightest at roughly magnitude 14, faint enough to need an 8-inch (200 mm) or larger telescope under dark skies and patience to track its slow motion against background stars over several nights. Ceres is the easy exception: at opposition it brightens to about magnitude 7, within reach of binoculars. The other three are realistic targets only for long-exposure astrophotography.

Small solar system bodies: asteroids, comets, Centaurs and TNOs

Everything orbiting the Sun that is not a planet, a dwarf planet, or a moon falls into one official catch-all category: the small solar system body (SSSB). The IAU coined this term in 2006, the same year it redefined “planet.” In plain terms, an SSSB is any other object held in solar orbit — too small to have pulled itself round, and never massive enough to clear its lane.

That single definition covers an enormous and varied population: the rocky asteroids of the inner system, the icy comets that blaze tails near the Sun, the Centaurs drifting between the giant planets, the near-Earth objects (NEOs) that cross our path, and most of the trans-Neptunian objects of the deep outer system. The sections that follow walk through each class in turn — first the asteroids, then the comets, then the frozen worlds beyond Neptune.

Asteroids

Asteroids are the rocky and metallic leftovers from the solar system’s birth 4.6 billion years ago. They never gathered into a planet, so today they orbit the Sun as a swarm of irregular, cratered worldlets ranging from pebble-sized rubble to bodies hundreds of kilometers across. Most live in the main asteroid belt between Mars and Jupiter, where Jupiter’s gravity stirred the region too violently for a planet to form.

Despite the “belt” name and crowded movie scenes, the region is mostly empty space. If you melted every main-belt asteroid into one ball, it would be smaller than Earth’s Moon, totaling only about 3% of the Moon’s mass. The largest single object, the dwarf planet Ceres, holds roughly a third of that total mass by itself.

Types of asteroids

Astronomers sort asteroids by what they are made of, which mostly tracks where in the belt they formed:

Centaurs: the comet-asteroid hybrids

Between the orbits of Jupiter and Neptune drifts a strange in-between population called the Centaurs — icy bodies on unstable, planet-crossing orbits that make them hybrids between asteroids and comets. They are named after the half-human, half-horse creatures of myth because they share traits of both families: rocky like an asteroid, but ice-rich like a comet, and some even grow faint comas when they swing close enough to the Sun.

Centaurs do not last long in astronomical terms. The giant planets’ gravity steadily flings them onto new paths, so they are thought to be former trans-Neptunian objects on their way to becoming short-period comets. The first one discovered, 2060 Chiron (found in 1977), behaves exactly like this — it was first catalogued as an asteroid, then surprised astronomers by sprouting a cometary coma. A handful of Centaurs, including Chariklo, even sport their own thin ring systems.

Trojans and near-Earth asteroids

Not every asteroid lives in the belt. Trojans share a planet’s orbit, parked at stable Lagrange points 60 degrees ahead of and behind it. Jupiter has more than a million Trojans larger than 1 km; NASA’s Lucy mission is touring several through the early 2030s, with its final flyby of the Patroclus-Menoetius binary set for 2033.

Near-Earth asteroids (NEAs), a key subset of the broader near-Earth objects, cross or approach Earth’s orbit, and the ones flagged as potentially hazardous get close enough to matter. Tracking and deflecting them is the job of planetary defense. NASA’s 2022 DART mission proved the concept by deliberately slamming a spacecraft into the moonlet Dimorphos and measurably shortening its orbit by about 32 minutes — the first time humans changed a celestial body’s path on purpose. We cover the threat in depth in our guide to what happens if an asteroid hits Earth.

Famous asteroids

• Apophis — a ~340 m (1,100 ft) stony asteroid that will pass within about 32,000 km (20,000 mi) of Earth’s surface on April 13, 2029, closer than our geostationary satellites. It poses no impact risk, but the naked-eye flyby will be a once-in-a-lifetime observing event for some two billion people across Europe, Africa, and western Asia.
• Bennu — a carbon-rich rubble pile visited by NASA’s OSIRIS-REx, which delivered a sample to Earth in 2023 containing the building blocks of life, including amino acids and all five DNA and RNA nucleobases.
• 16 Psyche — a giant metallic asteroid (~220 km / 140 mi) thought to be a battered planetary core; NASA’s Psyche spacecraft is en route for arrival in 2029.
• Vesta — the second-largest belt object and the brightest asteroid, occasionally visible to the naked eye; NASA’s Dawn mission orbited it in 2011–2012 before moving on to Ceres.

Observing difficulty: binoculars to small telescope. Vesta is the only asteroid that ever reaches naked-eye brightness (around magnitude 5.1 at a favorable opposition). Ceres, Pallas, and Juno are easy binocular targets near opposition, appearing as slow-moving “stars” that shift against the background over a night or two. Best time: each asteroid’s own opposition. Minimum aperture: binoculars for the brightest few, a 4-inch scope for fainter members. To confirm a catch, sketch or photograph the field, then compare an hour later — the dot that moved is your asteroid. For the full taxonomy, orbital maps, and a target list by season, see our complete guide to asteroids.

Comets

Comets are the solar system’s “dirty snowballs” — loose mixes of water ice, frozen gases, dust, and rock left over from the system’s birth 4.6 billion years ago. Most spend their lives frozen and invisible in the cold outer reaches. They only come alive when their orbits carry them close to the Sun. Astronomers have catalogued about 4,600 known comets to date, and the number rises every year as sky surveys deepen.

As a comet nears the Sun, its ice sublimates (turns straight from solid to gas). This releases gas and dust that form a glowing coma — a fuzzy atmosphere around the solid nucleus — and one or more tails.

A key fact worth remembering: a comet’s tails always point away from the Sun, not behind its direction of travel. The solar wind and sunlight push the material outward. So an outbound comet actually travels tail-first. Comets typically grow two tails — a bluish ion (gas) tail and a curved, whitish dust tail.

Where comets come from

Comets fall into two families based on how long they take to orbit the Sun:

Short-period comets loop through the inner solar system on a predictable schedule. Long-period comets dive in from the Oort Cloud on enormous, often one-time orbits, which makes them far harder to forecast.

Famous comets

• Halley’s Comet — the most famous of all, last seen in 1986 and returning at perihelion on 28 July 2061. It is the only short-period comet reliably visible to the naked eye from Earth, and the 2061 pass should be far brighter than 1986 because the comet will be on the same side of the Sun as we are.
• Comet Hale-Bopp — the “Great Comet of 1997,” so bright it stayed visible to the naked eye for a record 18 months (May 1996 to December 1997).
• Comet C/2022 E3 (ZTF) — the “green comet” that made its closest approach to Earth on 1 February 2023, its color caused by glowing diatomic carbon (C₂).
• Comet C/2023 A3 (Tsuchinshan-ATLAS) — a stunning naked-eye comet that wowed observers in October 2024, the brightest comet seen since Hale-Bopp.

A handful of visitors are not even from our solar system. 1I/’Oumuamua (2017) and 2I/Borisov (2019) were the first two confirmed interstellar objects — bodies flung in from other star systems, passing through once and leaving forever. A third, 3I/ATLAS, was confirmed in July 2025, showing that these alien visitors are turning up more often as our sky surveys improve.

Observing and photographing comets

Observing difficulty: unpredictable. A bright “great comet” may shine to the naked eye; most others need binoculars or a telescope. Best time: whenever a comet is near perihelion and well placed in a dark sky. Minimum aperture: none for a great comet, binoculars or a 4-inch scope for the rest. Comets are among the most rewarding — and most unpredictable — astrophotography targets, since a faint speck can brighten dramatically (or fizzle) with little warning. Because comets drift against the fixed stars, imagers track the comet’s motion across many short exposures, then stack on the nucleus to keep it sharp. From the southern hemisphere especially, a fresh discovery can mean racing to catch it over just a few clear nights.

For the full breakdown of comet types, upcoming apparitions, and a step-by-step imaging workflow, see our complete guide to observing and photographing comets.

Trans-Neptunian objects: the Kuiper Belt & Oort Cloud

A trans-Neptunian object (TNO) is any body that orbits the Sun at an average distance greater than Neptune, which sits at 30 astronomical units (AU). One AU is the Earth-Sun distance, about 150 million km (93 million miles). This frozen frontier holds the bulk of the solar system’s leftover building blocks, and astronomers have already cataloged more than 5,000 of them. For the full taxonomy and a deeper look at how these worlds were discovered, see our dedicated guide to trans-Neptunian objects and the icy outer solar system.

These distant worlds fall into three main regions, each farther and fainter than the last.

The Kuiper Belt (30–50 AU)

The Kuiper Belt is a doughnut-shaped ring of icy bodies stretching from Neptune’s orbit out to roughly 50 AU. Think of it as the asteroid belt’s bigger, colder cousin, made of rock and frozen volatiles like water, methane, and ammonia ice rather than mostly rock and metal.

This is where Pluto lives, alongside fellow dwarf planets Haumea and Makemake. The belt and its dynamic outer fringe also feed the short-period comets, the kind that loop back through the inner solar system in under 200 years, such as Comet 67P/Churyumov–Gerasimenko, the icy world visited by ESA’s Rosetta mission. When you read about a bright comet swinging past Earth, this region is often its starting point. (Halley’s Comet, by contrast, is a longer-traveling visitor that traces back to the far more distant Oort Cloud.)

The scattered disk

Just beyond and overlapping the Kuiper Belt lies the scattered disk, a sparse population of objects flung onto stretched, tilted orbits by Neptune’s gravity. Eris, the most massive known dwarf planet, is a scattered-disk object. These bodies can swing out to 100 AU or more before falling back toward the Sun. Most short-period comets are now thought to trace back to this restless region rather than the calmer main belt.

The Oort Cloud

Far beyond everything else lies the Oort Cloud, a vast spherical shell of perhaps trillions of icy bodies thought to surround the entire solar system. Unlike the flat, disk-shaped Kuiper Belt, the Oort Cloud wraps the Sun in all directions. Its inner edge may begin around 2,000 AU, and its outer reaches are estimated to extend to roughly 100,000 AU, on the order of 1.6 light-years, a sizable fraction of the way to the next star (Proxima Centauri lies about 4.2 light-years away).

No one has ever directly observed the Oort Cloud; its existence is inferred from the orbits of long-period comets, which take thousands to millions of years to circle the Sun. It marks the true gravitational edge of the solar system.

Sedna: a world of the deep

Sedna is one of the strangest objects ever found. This reddish dwarf-planet candidate never comes closer than about 76 AU and swings out to roughly 900 AU on an orbit that takes about 11,400 years to complete. Its extreme path suggests it belongs to a transitional zone between the scattered disk and the inner Oort Cloud, possibly shaped by a passing star early in the solar system’s history.

Observing difficulty: imaging-only. Even Pluto, the brightest, glows at only about magnitude 14 to 15, far too faint for the naked eye or binoculars. Capturing it requires an 8-inch (200 mm) or larger telescope, a sensitive camera, and a series of stacked exposures taken over several nights to reveal its slow drift against the stars. Best time: each object’s opposition, under a truly dark sky. From my own remote rig in Chile, confirming a TNO means blinking images night to night and watching for the single dot that moves. Eris is fainter still at about magnitude 19, and Sedna is fainter again near magnitude 21, both well beyond the reach of most backyard setups.

Is there a Planet Nine?

For more than a decade, astronomers have wondered whether a real ninth planet — a genuine giant, not Pluto — is hiding in the dark far beyond Neptune. The idea is known as Planet Nine, and while it is still unconfirmed, the evidence behind it is intriguing.

The hypothesis grew out of a strange pattern. A handful of the most distant trans-Neptunian objects, including Sedna, have orbits that are oddly clustered — tilted and pointed in the same general direction, as if something massive were herding them. In 2016, researchers proposed that an unseen super-Earth, perhaps five to ten times Earth’s mass, could explain that shepherding if it orbits the Sun somewhere around 400 to 800 AU out — far enough that it would be extraordinarily faint and easy to miss.

So far, no one has found it. Wide-sky surveys have ruled out many possible locations, and some astronomers argue the clustering could be an illusion caused by where we have looked, not by a hidden planet. The new Vera C. Rubin Observatory, which began its deep survey of the southern sky in 2025, is exactly the kind of instrument that could either spot Planet Nine or finally rule it out. Until then, the solar system officially has eight planets — but the door on a ninth is not fully closed.

Moons

Moons are natural satellites that orbit planets, dwarf planets, and even some asteroids. The solar system now holds more than 400 planetary moons (890+ counting moons of dwarf planets, asteroids and TNOs), and the count keeps climbing fast as deep surveys uncover swarms of small ones around the giant planets. They range from giant ocean worlds to lumpy captured rocks just a few kilometers wide.

Saturn alone leapfrogged every other planet in 2025, when the International Astronomical Union recognized a large batch of newly found moons. As of mid-2026 Saturn has roughly 274 known satellites, more than all the other planets combined, while Jupiter sits near 95. Earth, by contrast, has exactly one.

Our Moon shapes the tides, stabilizes our axis, and sets the rhythm of every night sky. We cover our own companion in depth on the dedicated Moon hub, from lunar phases to photographing craters along the terminator.

The most fascinating moons are the active, potentially habitable ones. Several rank among the best places to search for life beyond Earth.

Observing the moons: You do not need professional gear to see worlds beyond our own. Point any pair of binoculars at Jupiter and you will spot up to four tiny points of light strung in a line beside it. These are the Galilean moons (Io, Europa, Ganymede, and Callisto), the same four Galileo first sketched in January 1610.

Watch them across a few nights and they visibly shift position, sometimes ducking behind or in front of the planet. That nightly dance was the observation that helped overturn the idea of an Earth-centered cosmos. Titan is reachable too, glowing as a faint star near Saturn through a small telescope. From my remote rig in Chile, tracking those moons as they swing around the gas giants never gets old.

For a complete tour of every major satellite, including the ice volcanoes of the outer system and which moons you can actually capture with a backyard setup, explore our full guide to the moons of the solar system.

Meteors and meteor showers

A meteor is the streak of light you see when a tiny piece of space debris burns up in Earth’s atmosphere. The terms are easy to mix up, so here is the quick distinction:

Most meteors come from leftover material shed by comets and asteroids. A few are flecks chipped off the Moon or Mars by ancient impacts.

A meteor shower happens when Earth plows through a trail of dusty debris left behind by a comet (or, in one famous case, an asteroid). Each year our planet crosses the same streams on the same dates, so showers are predictable. The grains slam into the atmosphere at anywhere from about 11 to 72 km/s (25,000–160,000 mph) and flare up, all appearing to radiate from one point in the sky.

Two showers stand out for backyard observers:

• Perseids (peak around August 12–13) — warm summer nights and a zenithal hourly rate near 100 (most observers see 50–80 per hour) from comet 109P/Swift-Tuttle, which circles the Sun about every 133 years.
• Geminids (peak around December 13–14) — the year’s richest display, with a zenithal hourly rate of 120+, from the “rock-comet” asteroid 3200 Phaethon.

Observing difficulty: naked-eye, no gear. Meteor showers are the single best free astronomy event. You need no telescope, no binoculars, and no skill. Best time: after midnight on the peak night, with the radiant high and the Moon out of the sky. Just find a dark sky away from city lights, lie back, let your eyes adapt for 20–30 minutes, and look up. A reclining chair and a warm blanket beat any gadget.

For peak dates, hourly rates, radiant positions, and viewing tips for every major shower throughout the year, see our complete guide to meteor showers.

Where does the solar system end?

There is no single edge. The solar system fades out in stages, and where you draw the line depends on whether you mean the Sun’s wind or the Sun’s gravity.

The two boundaries sit thousands of times apart:

The heliopause is the edge of the heliosphere, the giant bubble the Sun inflates with its charged-particle wind. Out near 120 astronomical units (1 AU = the Earth-Sun distance), that wind finally loses to the gas and plasma drifting between the stars. NASA’s twin Voyager probes crossed it for real: Voyager 1 in August 2012 (at about 121 AU) and Voyager 2 in November 2018 (at about 119 AU), making them the first human-made objects to reach interstellar space. Both are still transmitting from beyond it today.

The gravitational edge lies far, far deeper. Beyond the Kuiper Belt and scattered disc sits the Oort Cloud, a vast spherical shell of icy bodies that stretches out to roughly 100,000 AU, about 1.6 light-years, or more than a third of the way to the next star. This is the true outer limit, the launching ground for long-period comets that fall in toward the Sun over millions of years.

So which is the “end”? By the solar wind, you leave at the heliopause. By gravity, you are not truly free of the Sun until you clear the Oort Cloud, a journey that would take even Voyager tens of thousands of years.

The state of solar-system exploration (2026)

The hero image at the top of this page is the famous Voyager montage — and the spacecraft that took those pictures are still working. More than four decades after launch, our robotic explorers have spread across the solar system and beyond, and 2026 finds several of them at extraordinary milestones.

The Voyagers are in interstellar space. Voyager 1 and Voyager 2, launched in 1977, have both crossed the heliopause and now transmit faint signals from beyond the Sun’s bubble of wind. Voyager 1 is the most distant human-made object ever, around 172 AU from the Sun in 2026 — so far that its radio signal, traveling at the speed of light, takes nearly a full day to reach Earth. Their power is fading, but both are expected to keep sending data on the interstellar environment for a few more years.

New Horizons is deep in the Kuiper Belt. After its history-making flyby of Pluto in 2015 — which gave us the heart-shaped nitrogen-ice plain and the first sharp maps of that world — NASA’s New Horizons probe kept going. In 2019 it flew past the small, two-lobed Kuiper Belt object Arrokoth, the most distant object ever explored up close. It is still cruising outward today, studying the dust and particle environment of the outer system.

JWST is doing solar-system science. The James Webb Space Telescope, best known for peering at the early universe, has also become a powerful tool for studying our own neighborhood. It has imaged the giant planets in fresh detail — capturing Neptune’s faint rings more clearly than anything since Voyager 2, tracking storms and auroras on Jupiter, and probing the atmospheres and small moons of the outer worlds. Webb also studies asteroids, comets, and trans-Neptunian objects, adding a new layer to what the flyby missions began.

Together with active orbiters and sample-return missions, these spacecraft mean the solar system is being explored more intensely now than at any time in history. For the science behind the targets they visit, follow the links throughout this guide — and to learn more about how NASA and ESA frame this work, see NASA’s solar system overview.

How to observe and photograph the solar system

The best part of the solar system is that you can see most of it yourself. You do not need a remote observatory to start. You need clear skies, a little patience, and a sense of where to point.

This is where a hub like NASA or Wikipedia stops and a real observer begins. Below is a tiered roadmap based on how I actually work targets, from a first telescope to my remote rig at Deepsky Chile (an Alluna 12.5″ Ritchey-Chretien on a Paramount MX+ with an SBIG STL-11000). You can read more about that setup and my background on the about page.

Three difficulty tiers

Every solar-system object falls into one of three rough tiers of effort. Start at Tier 1 and work down.

Tier 1 is genuinely easy. Saturn’s rings through even a small telescope are a moment people never forget. Jupiter’s four Galilean moons — the same ones Galileo spotted in 1610 — shift position every single night, so two sketches a few hours apart will show them move. Bright comets and meteor showers need no gear at all, just a dark sky and a reclined chair.

Tier 2 starts when you add tracking. A motorized mount keeps a planet centered while you shoot thousands of frames. Software then stacks the sharpest ones, a technique called lucky imaging that freezes the brief moments of steady air. This is how backyard astronomers pull cloud belts off Jupiter and polar ice off Mars at opposition.

Tier 3 is where the solar system gets quiet and faint. Uranus and Neptune show as small blue-green disks only at high magnification on a steady night; you typically need a 3-to-4-inch scope and 150x or more to resolve them into more than a point. Pluto never resolves at all. At around 14th magnitude it takes roughly an 8-inch telescope under a dark sky, and you confirm it by photographing the same star field across two or three nights and watching one “star” drift. Catching a faint asteroid works the same way. This tier rewards patience over money.

Tools that take the guesswork out

Three free calculators on this site solve the planning problems that trip people up most.

• Field of view simulator — Before you buy or shoot, see exactly how big a target lands on your sensor with your scope. It tells you whether Saturn will be a tiny dot or fill the frame, and whether a comet’s tail will fit. This prevents the most common beginner mistake: the wrong focal length for the target.
• Sub-exposure calculator — For fainter objects and wide-field comet shots, this finds the ideal length for each exposure so you swamp sensor noise without blowing out highlights or wasting clear-sky time.
• Astrophotography calculator hub — The all-in-one home for sampling, exposure, and imaging math when you want every tool in one place.

Practical tips that matter more than gear

A few hard-won habits separate frustrating nights from great ones.

• Light pollution caps the faint stuff. The Moon and bright planets punch through city glow, but comets, asteroids, and Uranus/Neptune need real darkness. Check a light-pollution map and, for the faint targets, plan a trip to a darker site.
• Steady seeing beats raw aperture for planets. A small scope on a calm, stable night will show more Jupiter detail than a giant scope on a turbulent one. “Seeing” — how still the air is — is the limiting factor for planetary work, not how much light you gather.
• Learn the ecliptic. The Sun, Moon, and every planet ride the same arc across the sky, called the ecliptic. Once you know that line, you always know roughly where to look, and you can spot when a planet is well placed for the night.
• Time it right. Outer planets are biggest and brightest at opposition — Mars, for example, reaches opposition only about every 26 months. Mercury and Venus only show well near their greatest elongation from the Sun. A good calendar app or planetarium program tells you when.

Master Tier 1 first. The skills and habits you build on the Moon and the bright planets are exactly the ones you carry down into the faint, rewarding depths of Tier 3.

Best targets for beginners

New to a telescope? Start here. These six targets are bright, easy to find, and deliver a real “wow” on your very first night — no dark sky or fancy gear required. Work down the list in order; each one builds your confidence for the next.

1. The Moon — The best first target, full stop. Even cheap binoculars reveal craters, mountains, and the stark shadow line (the terminator) where sunrise sweeps across the surface. A first-quarter phase shows far more detail than a full Moon, because the side-lighting hits the surface at a shallow angle and throws every crater and ridge into sharp relief — at full Moon the sunlight comes straight down and the view looks flat and washed out. Our complete guide to observing and photographing the Moon walks through phases and the best nights to look.
2. Jupiter — Point any small scope at the brightest “star” in that part of the sky and you will see a tiny disk flanked by up to four bright dots: the Galilean moons (Io, Europa, Ganymede, Callisto), which visibly shift position from night to night. With steady air, the two main cloud belts emerge across the disk. See when and how in our Jupiter observing and imaging guide.
3. Saturn — The target that makes people gasp out loud. Even a modest 60-80 mm telescope at 50x or more resolves the rings as a separate structure circling the planet — the single most memorable view in backyard astronomy. (Note that through 2025-2026 the rings sit nearly edge-on, so they look like a thin line; they open wider again over the following years.) The Saturn sub-hub covers ring tilt and the best apertures.
4. Venus — The dazzling “evening star” (or morning star) shows a tiny disk that runs through phases just like the Moon, from a fat gibbous to a slim crescent as it swings around the Sun. Catch it near greatest elongation, when it sits farthest from the Sun’s glare and shows a crisp half-lit “quarter” face. It is a quick, satisfying win even from a light-polluted balcony.
5. A meteor shower — No equipment needed at all — just your eyes, a reclining chair, and a dark-ish sky. Reliable annual showers like the Perseids (peaking around August 12-13) and Geminids (peaking around December 13-14) can deliver dozens of “shooting stars” per hour from a dark site at their peak. Check dates and viewing tips in our meteor showers guide.
6. A bright comet (when one appears) — Once or twice a decade, on average, a comet bright enough for binoculars or even the naked eye graces our skies, trailing a ghostly tail. They are unpredictable, so watch the news and our comets sub-hub for alerts when the next one swings by.

A quick tip from the field: start with the Moon and planets, which punch through light pollution and even shine from a city backyard. Faint deep-sky objects and comets reward darker skies and patience — but you don’t need either to get hooked tonight.

Every object above has its own dedicated observing section in the linked sub-guides, with specific advice on the best time to look, the minimum aperture you’ll want, and how to start photographing it. Pick one clear night, point your scope, and you’re an observer.

Solar system records and fun facts

Hungry for more cosmic trivia? Dig into our deep dive on the secrets of the solar system.

Our cosmic neighborhood holds some jaw-dropping extremes. Here are the record-holders worth knowing — and for backyard observers, several are visible from your own yard with modest gear.

A few standouts deserve a closer look:

• Hottest, not closest. Venus runs hotter than Mercury despite sitting farther from the Sun. Its thick carbon-dioxide atmosphere traps heat in a runaway greenhouse effect, holding the surface near 465 °C (~870 °F) day and night — hot enough to melt lead.

• A moon bigger than a planet. Ganymede, the largest of Jupiter’s Galilean moons, measures 5,268 km (3,273 mi) across — wider than the planet Mercury. Spot all four Galilean moons with even cheap binoculars on any clear night — they shift position from hour to hour as they circle the giant.

• The mountain that dwarfs Everest. Olympus Mons on Mars rises about 22 km (13.6 mi), roughly 2.5 times taller than Everest, and spreads as wide as France. Low gravity and a stationary crust — Mars has no plate tectonics — let lava stack in one spot for billions of years, building the volcano to such size.

• Io, the pizza moon. Jupiter’s innermost large moon is the most volcanically active world we know, with sulfur plumes erupting hundreds of kilometers high. Tidal flexing from Jupiter’s immense gravity — and tugs from neighboring moons Europa and Ganymede — keeps its interior molten.

• Neptune’s once-around milestone. Discovered in 1846, Neptune takes about 165 Earth years to circle the Sun — so it completed its first full orbit since discovery only in July 2011. Most people alive today will never see it finish another.

From Saturn’s glorious rings to the Sun holding 99.86% of the system’s mass, the solar system never runs short of superlatives.

Frequently asked questions

How many objects are in the solar system?
Astronomers have catalogued more than 1.4 million tracked asteroids, about 4,600 known comets, more than 400 planetary moons (890+ counting moons of dwarf planets, asteroids and TNOs), 8 planets, and 5 official dwarf planets, all orbiting one star. The true count runs into the trillions once you include the icy bodies of the Kuiper Belt and the distant Oort Cloud, most of which we have never seen.

What are small solar system bodies?
“Small solar system body” is the official IAU 2006 catch-all for everything orbiting the Sun that is neither a planet nor a dwarf planet nor a moon. It covers asteroids, comets, Centaurs, near-Earth objects, and most trans-Neptunian objects. Our deep dives on asteroids and the asteroid belt, comets, and trans-Neptunian objects break each class down further.

What is the order of the planets from the Sun?
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, then Neptune. The asteroid belt sits between Mars and Jupiter, with the Kuiper Belt and Oort Cloud beyond Neptune.

How do you remember the order of the planets?
Use the classic mnemonic “My Very Educated Mother Just Served Us Nachos.” The first letter of each word matches a planet in order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Older versions ended in “Nine Pizzas” for Pluto, but Pluto was reclassified as a dwarf planet in 2006 and dropped off the list.

Is there a Planet Nine?
Possibly, but it is unconfirmed. The Planet Nine hypothesis proposes an unseen super-Earth, perhaps five to ten times Earth’s mass, orbiting roughly 400 to 800 AU from the Sun. The idea comes from the strangely clustered orbits of several distant trans-Neptunian objects, which look as though a massive body is herding them. No such planet has been found yet, and new surveys like the Vera C. Rubin Observatory should either spot it or rule it out in the coming years.

Is Pluto part of the solar system?
Yes. Pluto is still very much part of the solar system; it was simply reclassified from planet to dwarf planet by the IAU in 2006. You can read the full story of that demotion on our Pluto sub-hub.

How old is the solar system?
The solar system is about 4.6 billion years old. It formed from the gravitational collapse of a giant molecular cloud, with the Sun and planets taking shape over the following few tens of millions of years.

Where does the solar system end?
There is no single fence. The heliopause, where the Sun’s particle wind meets interstellar space, sits roughly 18 billion km (about 11 billion mi) out, while the Sun’s gravity still holds the Oort Cloud as far as 1.6 light-years away, which many astronomers treat as the true edge.

What is the biggest object in the solar system?
The Sun, by an enormous margin. It holds 99.86% of all the mass in the solar system and could swallow more than 1.3 million Earths. Among the planets, Jupiter is the largest.

Can you see the planets without a telescope?
Yes. Mercury, Venus, Mars, Jupiter, and Saturn are all visible to the naked eye and have been watched since ancient times. Venus and Jupiter are bright enough to spot even from a city, while Uranus and Neptune need binoculars or a telescope.

What is the best planet to photograph for a beginner?
Jupiter and Saturn are the easiest and most rewarding first targets. Both are bright, sit well above the horizon for months around opposition, and reveal cloud bands or rings through a modest 4-6 inch telescope and a simple planetary camera. The field-of-view simulator helps you frame them before you shoot.

How many planets have rings?
All four giant planets have ring systems: Jupiter, Saturn, Uranus, and Neptune. Saturn’s are by far the brightest and the only ones easily seen from a backyard telescope; the other three are faint and dusty.

What is the hottest planet in the solar system?
Venus, not Mercury. A runaway greenhouse atmosphere of thick carbon dioxide traps heat and pushes its surface to about 465 °C (around 870 °F), hot enough to melt lead, even though Mercury sits closer to the Sun.

Which planet has the most moons?
Saturn, with roughly 274 confirmed moons as of mid-2026, well ahead of Jupiter at about 95. Most of these are tiny, irregular chunks of rock and ice only a kilometre or two across, found in recent deep surveys rather than seen through a backyard scope. Explore the whole family on our moons of the solar system hub.

How far is the nearest star?
After the Sun, the nearest star is Proxima Centauri, about 4.2 light-years away, or roughly 40 trillion km (25 trillion mi). Even at the blistering speed of NASA’s Voyager probes, the trip would take more than 70,000 years.

About the author: Hamza has been an astrophotographer since 2008 and operates a remote imaging observatory at Deepsky Chile, using an Alluna 12.5″ Ritchey-Chrétien telescope on a Paramount MX+ mount with an SBIG STL-11000 camera. He shares his work and the night sky of the southern hemisphere on Instagram @stellar.nomads — read more on the about page.

Ready to start imaging these worlds yourself? Plan your first target with the free field-of-view simulator, dial in your exposures with the sub-exposure calculator, or open the all-in-one astrophotography calculator hub — then pick a clear night and point your scope.