M31 / NGC224
Andromeda Galaxy
Object Info

The "Andromeda" galaxy is the closest galaxy of comparable size to our "Milky Way." It is the largest member of the local group of about 20 galaxies. It is about the same size as our "Milky Way" galaxy, containing several hundred billion stars. It has two satellite galaxies (see labeled image) and hundreds of globular star clusters in its galactic halo.

M31's two bright satellite galaxies are M32 / NGC221 and M110 / NGC205, both classified as elliptical. There are also two faint companion galaxies, NGC147 and NGC185 nearby in Cassiopia.

Astronomers classify galaxies according to structure. Spiral galaxies are flat disks of stars, gas and dust while elliptical galaxies are spherical or ellipsoidal masses of stars, usually with very little gas and dust. References to galaxies usually include an upper case letter S for sprial, E for elliptical or I for irregular followed by one or more letters and/or numbers which further specify structure. An (Sb) type is a barred spiral, an (E2) is a flattened elliptical with a small nucleus, etc. Refer to an astronomy textbook or the internet for details.