Andromeda Galaxy

Andromeda Galaxy M31, can't recall the source
Andromeda Galaxy M31
The Andromeda Galaxy, M31, is a spiral galaxy ~2.5 million light-years away (see doi:10.1086/499161) in the constellation Andromeda.
 
A galaxy is a large collection of stars, gas and dust moving as a identifiable, isolated system under the influence of gravity. Our own Milky Way and the Andromeda galaxy will start to collide about four billion years from now, merging over the following two billion years -- NASA. (It is thought that the earth is about 4.5 billion years old, and that life on earth originated over three billion years ago -- various.)
 
A constellation is a group of stars that appear to be close in the (2D) sky, but are likely to be far apart in 3D.
 
In Greek mythology, Andromeda was chained to a rock and left to be eaten by a sea monster; Perseus rescued her.