The Planets of the Solar System: A Complete Guide

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.