This is color image of the Andromeda galaxy, also known as Messier 31. It is the nearest
large spiral galaxy to our own Milky Way galaxy, and at a distance of only (!) 2 million
light years, is part of what is called the "Local Group" of galaxies. (Note: the stars
scattered more or less uniformly over the face of this picture are relatively nearby stars
in OUR galaxy that we must look beyond (way beyond!) to see M31.) Since we are viewing
M31 at an oblique angle, it's spiral structure is not entirely obvious.
Color pictures such as this are often made by combining separate photographs taken with
different color filters. In this picture, the blue light shows regions where hot, young
stars have formed, which is mostly out on the edges (in the spiral arms). Pink and white
regions toward the center show places where mostly older, cooler stars reside in M31.
The dark, blotchy regions show where giant clouds of gas and dust ring the spiral arms.