spiral galaxy

References

Images & Videos

M64, spiral galaxy in Coma Berenices.

M81, spiral galaxy in Ursa Major

Figure 7: Omega Centauri (M3), the most imposing globular cluster in the Milky Way Galaxy.

M101, spiral galaxy in Ursa Major

The small spiral galaxy NGC 7742, a Type 2 Seyfert galaxy, as seen by the Hubble Space Telescope.

What are the three types of galaxies?

spiral galaxy

astronomy

Also known as: spiral nebula

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July 14, 2026

Quick Summary

M31 — M31 M31, Andromeda Galaxy

A spiral galaxy is a type of galaxy characterized by a central nucleus or barred structure from which curved arms of higher luminosity extend. These galaxies possess circular symmetry, featuring a bright nucleus surrounded by a thin outer disk, with a superimposed spiral structure. The arms themselves are generally thought to follow a logarithmic spiral form.123

Spiral galaxies are divided into two main classes: normal spirals, where arms emanate from the nucleus, and barred spirals, which have a linear bar structure with arms unwinding from its ends. The arms and disk of a spiral system appear blue, while the central areas are red. The Milky Way Galaxy is an example of a spiral galaxy, with its structure including a nucleus, central bulge, disk, spiral arms, and a halo.245

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galaxy
Spiral galaxies
Spirals are characterized by circular symmetry, a bright nucleus surrounded by a thin outer disk, and a superimposed spiral structure. They are divided into two parallel classes: normal spirals and barred spirals. The normal spirals have arms that emanate from the nucleus, while…
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Spirals are characterized by circular symmetry, a bright nucleus surrounded by a thin outer disk, and a superimposed spiral structure. They are divided into two parallel classes: normal spirals and barred spirals. The normal spirals have arms that emanate from the nucleus, while…
Read More

nebula
In a spiral galaxy the interstellar medium makes up 3 to 5 percent of the galaxy’s mass, but within a spiral arm its mass fraction increases to about 20 percent. About 1 percent of the mass of the interstellar medium is in the form of “dust”—small solid…
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In a spiral galaxy the interstellar medium makes up 3 to 5 percent of the galaxy’s mass, but within a spiral arm its mass fraction increases to about 20 percent. About 1 percent of the mass of the interstellar medium is in the form of “dust”—small solid…
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astronomy
Study of other galaxies and related phenomena
Spiral galaxies—of which the Milky Way system is a characteristic example—tend to be flattened, roughly circular systems with their constituent stars strongly concentrated along spiral arms. These arms are thought to be produced by traveling density waves, which compress and expand the galactic material. Between…
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Spiral galaxies—of which the Milky Way system is a characteristic example—tend to be flattened, roughly circular systems with their constituent stars strongly concentrated along spiral arms. These arms are thought to be produced by traveling density waves, which compress and expand the galactic material. Between…
Read More

Edwin Hubble
…the problem of the so-called spiral nebulae, objects he had investigated for his doctorate. The status of the spirals (as they were widely known) was then unclear. Were they distant star systems (galaxies in current terminology) comparable to the Milky Way Galaxy, or were they clouds of gas or sparse…
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…the problem of the so-called spiral nebulae, objects he had investigated for his doctorate. The status of the spirals (as they were widely known) was then unclear. Were they distant star systems (galaxies in current terminology) comparable to the Milky Way Galaxy, or were they clouds of gas or sparse…
Read More