M31: The Andromeda
Galaxy
From NASA’s Astronomy Picture of the Day
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 image of M31 was taken with a standard
camera through a small telescope. Much about M31 remains unknown, including how it acquired its
unusual double-peaked center.
