Quick answer: There are four main galaxy types — spiral, elliptical, lenticular and irregular — first organised by Edwin Hubble in 1926. Spirals have graceful arms, ellipticals are smooth balls of old stars, lenticulars sit between the two, and irregulars have no clear shape. A fifth group, peculiar galaxies, covers colliding and distorted systems.
The main galaxy types are spiral, elliptical, lenticular and irregular — a scheme astronomers have used for a century. But that tidy list hides a universe of variety, from barred pinwheels to giant elliptical blobs a thousand times more massive than our own Milky Way. This guide walks through every type, shows you what each one really looks like, and — because I photograph these objects for a living — points out which galaxy types are the best targets for your own telescope.
I’ve spent years imaging galaxies from a remote observatory in the Atacama Desert in Chile, so alongside the textbook definitions you’ll get an honest sense of what these objects look like through an eyepiece versus in a long-exposure photograph. The difference is bigger than most beginners expect.
Table of contents
- What is a galaxy?
- How many types of galaxies are there?
- How galaxies are classified: the Hubble tuning fork
- Spiral galaxies
- Elliptical galaxies
- Lenticular galaxies
- Irregular galaxies
- Peculiar and interacting galaxies
- Active galaxies and quasars
- What type of galaxy is the Milky Way?
- How galaxies change type over time
- The best galaxy types to photograph
- Frequently asked questions
What is a galaxy?
A galaxy is a vast, gravitationally bound system of stars, gas, dust and dark matter. The smallest dwarf galaxies hold a few million stars; giants like the Milky Way hold hundreds of billions. Our own galaxy is just one of an estimated two trillion galaxies in the observable universe, according to NASA.
Before we sort galaxies into types, it helps to know what separates a galaxy from the other fuzzy objects you’ll read about. A nebula is a single cloud of gas and dust inside a galaxy. A star is one Sun. A galaxy is the whole city — billions of stars plus all the nebulae between them. Classifying galaxies is really about classifying their shapes, and shape turns out to tell us a surprising amount about a galaxy’s age and history.
How many types of galaxies are there?
There are four main types of galaxies: spiral, elliptical, lenticular and irregular. Astronomers often add a fifth catch-all category — peculiar galaxies — for systems distorted by collisions and gravity. Here is the quick version before we dig into each one:
- Spiral galaxies — flat, rotating disks with curved arms and a central bulge. The Milky Way is one.
- Elliptical galaxies — smooth, round-to-oval swarms of mostly old stars, with little gas or new star formation.
- Lenticular galaxies — a disk with a bulge but no visible arms; a halfway house between spirals and ellipticals.
- Irregular galaxies — no organised shape at all, often small and rich in gas.
- Peculiar galaxies — galaxies warped or merging, such as colliding pairs and ring galaxies.
Roughly two-thirds of large, bright galaxies in the nearby universe are spirals, but ellipticals dominate the crowded centres of galaxy clusters. Irregulars are common but faint, so they’re under-represented in the images you usually see. Each type is defined by its structure, which is exactly what the Hubble classification captures.
How galaxies are classified: the Hubble tuning fork
Galaxies are classified mainly by their shape using the Hubble sequence, a diagram Edwin Hubble introduced in 1926. Because of its shape, it’s nicknamed the “tuning fork.” It’s still the first thing every astronomy student learns about galaxy morphology.
On the left of the fork sit the elliptical galaxies, labelled E0 (nearly round) through E7 (most flattened). The fork then splits into two prongs of spiral galaxies. The top prong holds ordinary spirals (Sa, Sb, Sc) and the bottom prong holds barred spirals (SBa, SBb, SBc), where the arms unwind from a straight bar of stars. The letters a, b and c describe how tightly the arms are wound and how big the central bulge is. Lenticular galaxies (S0) sit at the junction where the fork divides.
Hubble once thought this diagram showed galaxies evolving from left to right, so ellipticals are still called “early-type” and spirals “late-type.” We now know that’s backwards — the terms survive out of habit, not because ellipticals are literally younger. Modern surveys like the Hubble Space Telescope archive and citizen-science projects such as Galaxy Zoo have classified millions of galaxies this way, confirming that Hubble’s simple scheme still captures the big picture.
Spiral galaxies
A spiral galaxy is a flattened, rotating disk of stars, gas and dust with curved arms winding out from a bright central bulge. They are the most photogenic galaxy type and the one most people picture when they hear the word “galaxy.”
The spiral arms are not solid structures. They’re waves of compression sweeping through the disk, piling up gas that then collapses into bright new stars. That’s why the arms glow blue — they’re studded with hot, young stars and pink star-forming nebulae. The bulge in the middle, by contrast, holds older, redder stars. The famous Whirlpool Galaxy (Messier 51) shown above is a textbook “grand design” spiral with two clean, sweeping arms.
Spirals are still actively forming stars, spin at hundreds of kilometres per second, and are held together by huge halos of dark matter — the invisible mass first inferred from galaxy rotation by Vera Rubin. Popular examples for stargazers include the Whirlpool (M51), the Pinwheel (M101) and our neighbour the Andromeda Galaxy (M31).
Barred spiral galaxies
A barred spiral galaxy is a spiral whose arms trail from the ends of a straight bar of stars crossing the core, rather than winding directly from the centre. About two-thirds of spiral galaxies — including the Milky Way — are barred, so this is the most common spiral sub-type of all.
The bar is thought to act like a cosmic funnel, channelling gas inward to feed star formation and, in many galaxies, a central supermassive black hole. NGC 1300, pictured above, is one of the most perfect barred spirals known, its bar stretching more than 100,000 light-years tip to tip.
Elliptical galaxies
An elliptical galaxy is a smooth, featureless swarm of stars shaped like a ball or a rugby ball, with no disk and no spiral arms. Their stars orbit in random directions rather than in an orderly rotating plane, which is why they look like a fuzzy glow that fades gently at the edges.
Ellipticals are the retirement homes of the galaxy world. They contain mostly old, red stars, very little cold gas, and almost no ongoing star formation — they long ago used up or lost their raw material. They range enormously in size, from tiny dwarf ellipticals to monsters like M87 (above), a giant elliptical at the heart of the Virgo Cluster that hosts the first black hole ever photographed.
Most giant ellipticals are believed to be the end product of galaxy mergers: when two spirals collide, their neat disks are scrambled into a single rounded blob. That’s why ellipticals cluster in dense environments where collisions are frequent. In a telescope they’re the least dramatic galaxy type — a soft oval with no detail — but their sheer scale makes them scientifically fascinating.
Lenticular galaxies
A lenticular galaxy (type S0) is a disk galaxy with a central bulge but no spiral arms — a genuine hybrid that shares features with both spirals and ellipticals. The name comes from their lens-like shape when seen edge-on, as in NGC 5866, the Spindle Galaxy, above.
Like spirals, lenticulars have a flattened, rotating disk. Like ellipticals, they’re dominated by old stars and have used up most of their star-forming gas. Astronomers think many lenticulars are “faded” spirals that ran out of gas, or spirals stripped of their gas by the hot environment inside a galaxy cluster. They sit at the fork of the Hubble diagram precisely because they blur the line between the two great galaxy families.
Irregular galaxies
An irregular galaxy has no regular shape — no disk, no bulge, no symmetry. These are usually small, gas-rich galaxies bursting with new stars, and they don’t fit anywhere on the Hubble tuning fork. NGC 1427A, above, is being pulled out of shape as it plunges through a galaxy cluster.
The two most famous irregular galaxies are the Large and Small Magellanic Clouds, satellite galaxies of the Milky Way that are easily visible to the naked eye from the Southern Hemisphere. Many irregulars got their chaotic look from a near-miss or collision with a bigger neighbour, whose gravity tore their structure apart. Because they’re small and faint, irregulars are the hardest of the main galaxy types to photograph well — but they’re forming stars at a furious rate, making them important laboratories for studying how galaxies grow.
Peculiar and interacting galaxies
Peculiar galaxies are galaxies whose shapes have been warped by gravity, usually because they’re colliding or merging with another galaxy. They’re not really a separate branch of the family tree so much as a snapshot of galaxies caught mid-transformation. The Antennae Galaxies, above, are two spirals in the act of merging, their collision flinging out long “tidal tails” of stars and igniting a firestorm of new star birth.
This category includes ring galaxies (created when a small galaxy punches straight through the centre of a larger one), galaxies with polar rings, and objects catalogued in Halton Arp’s famous Atlas of Peculiar Galaxies. Galaxy collisions are how the universe builds its biggest galaxies — even the Milky Way is on a collision course with Andromeda, though not for another four billion years.
Active galaxies and quasars
Some galaxies are classified not by their shape but by what’s happening at their core. An active galaxy has a compact central region — an active galactic nucleus, or AGN — that blazes with more energy than all its stars combined, powered by gas spiralling into a supermassive black hole.
These active types cut across the shape-based categories:
- Quasars — the most luminous AGN, so bright they were first mistaken for stars; they mark feeding black holes in the distant, early universe.
- Seyfert galaxies — usually spirals (like nearby Messier 106) with a bright, active nucleus but an otherwise normal disk.
- Radio galaxies — often giant ellipticals firing enormous jets of plasma that glow at radio wavelengths.
- Blazars — active galaxies whose jet points almost straight at Earth, making them wildly variable in brightness.
Astronomers now think most big galaxies host a sleeping supermassive black hole, and that “active” and “quiet” are just phases the same galaxy passes through when fresh gas falls in.
What type of galaxy is the Milky Way?
The Milky Way is a barred spiral galaxy, classified as type SBbc. It has a flat disk of gas and stars, a straight bar of stars through the centre, and two major spiral arms plus several minor ones. It measures roughly 100,000 light-years across and contains an estimated 100–400 billion stars.
We can’t photograph our own galaxy from the outside, so its exact structure was pieced together by mapping the motion of stars and gas from within. That’s how astronomers confirmed the central bar in the 2000s. At the very centre sits Sagittarius A*, a supermassive black hole about four million times the mass of the Sun. The bright band of the Milky Way you see on a dark night is simply our view along the plane of that disk from our position about two-thirds of the way out.
How galaxies change type over time
Galaxy types are not permanent labels — they’re stages in a long story of growth and collision. Over billions of years, a galaxy can change type entirely, and understanding that evolution is one of the frontiers of modern cosmology.
The leading picture goes like this: gas-rich spirals form first from the collapse of cold gas. When two spirals collide, their disks are destroyed and they merge into a single elliptical. Spirals that drift into a dense cluster and lose their gas can fade into lenticulars. In other words, the Hubble sequence isn’t an evolutionary track from one end to the other — galaxies move around it as mergers and environment reshape them. The James Webb Space Telescope is now catching galaxies in the act, revealing that the earliest galaxies were smaller, clumpier and more chaotic than the tidy spirals and ellipticals of today.
The best galaxy types to photograph
If you want to photograph galaxies yourself, the type matters enormously. After years of imaging them from Chile, here’s my honest ranking of which galaxy types reward a backyard setup — and which will disappoint you.
- Bright face-on spirals are the best targets. The Whirlpool, the Pinwheel and Bode’s Galaxy (M81) show arms, colour and dust lanes even in modest gear. Their structure is what makes galaxy photos pop.
- Edge-on spirals and lenticulars, like the Needle Galaxy (NGC 4565), are dramatic thanks to their knife-thin profiles and dark dust lanes.
- Bright ellipticals, such as M87 or M49, are easy to capture but visually plain — a smooth glow with no detail, so they’re less rewarding.
- Irregulars and dwarfs are the toughest: small, faint and low in contrast. Save them for dark skies and long integration times.
Whatever the type, galaxies are faint, so success comes down to dark skies, accurate tracking and total exposure time — not raw aperture. Before a session, use our telescope field of view calculator to check a galaxy will actually fit your frame, and the astrophotography calculator to plan exposures. New to deep-sky imaging? Start with our astrophotography fundamentals guide and the right type of telescope for the job.
One reality check: through the eyepiece, almost every galaxy looks like a faint grey smudge. All the colour and spiral detail you see online only emerges in a stacked, long-exposure photograph. That gap between eye and camera is the whole reason astrophotography exists.
Frequently asked questions
What are the 4 main types of galaxies?
The four main types of galaxies are spiral, elliptical, lenticular and irregular. Spirals have arms and a disk, ellipticals are smooth balls of old stars, lenticulars are disks without arms, and irregulars have no defined shape. Distorted, colliding galaxies form a fifth “peculiar” group.
What is the most common type of galaxy?
Among the large, bright galaxies we can easily see, spiral galaxies are the most common, making up roughly two-thirds of them. If you count the faint dwarf galaxies, though, small irregular and dwarf elliptical galaxies vastly outnumber every other type in the universe.
What type of galaxy do we live in?
We live in the Milky Way, a barred spiral galaxy about 100,000 light-years across containing 100–400 billion stars. Our Sun sits roughly two-thirds of the way out from the centre, in a minor spiral arm called the Orion Arm.
How did Edwin Hubble classify galaxies?
Edwin Hubble classified galaxies by shape in 1926 using his “tuning fork” diagram: ellipticals on the handle, ordinary and barred spirals on the two prongs, and lenticulars at the junction. Astronomers still use this Hubble sequence today.
What is the difference between a spiral and elliptical galaxy?
A spiral galaxy is a flat, rotating disk with arms and active star formation, full of young blue stars and gas. An elliptical galaxy is a rounded swarm of mostly old red stars with little gas and almost no new stars. Spirals spin in an orderly plane; ellipticals’ stars orbit in random directions.
Can you see other galaxies with a telescope?
Yes. The Andromeda Galaxy is visible to the naked eye from a dark site, and dozens of galaxies show up in a small telescope as faint grey smudges. Their colour and spiral detail, however, only appear in long-exposure photographs, not through the eyepiece.
Keep exploring
Galaxies are the natural next step once you understand their building blocks. Read up on what a star is and what a nebula is, meet the astronomers who mapped the cosmos on our famous astronomers hub, or see how galaxies fit into the big picture in our guide to cosmology. Ready to point a camera at one? The Whirlpool Galaxy is the perfect first target.