Explanation:
Andromeda is the nearest major
galaxy to our own
Milky Way Galaxy.
Our Galaxy is thought to look much like
Andromeda.
Together these two galaxies dominate the
Local Group of galaxies.
The diffuse light from
Andromeda
is caused by the hundreds of billions of
stars that compose it.
The several distinct stars that surround
Andromeda's image
are actually stars in
our Galaxy
that are well in front of the background object.
Andromeda is
frequently referred to as M31 since it is the 31st
object on
Messier's list of diffuse sky objects.
M31 is so distant it takes
about two million years for light to reach us from there.
Although visible without aid, the
above image of M31 is a digital mosaic of
20 frames taken with a small telescope.
Much about M31
remains unknown, including how the center acquired
two nuclei.
