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M31, the Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years away in the constellation Andromeda. It is also known as Messier 31, or NGC 224. Andromeda is the nearest spiral galaxy to the Milky Way, but not the closest galaxy overall. It gets its name from the area of the sky in which it appears, the Andromeda constellation, which was named after the mythological princess Andromeda. Andromeda is the largest galaxy of the Local Group, which consists of the Andromeda Galaxy, the Milky Way Galaxy, the Triangulum Galaxy, and about 30 other smaller galaxies. Although the largest, Andromeda may not be the most massive, as recent findings suggest that the Milky Way contains more dark matter and may be the most massive in the grouping. The 2006 observations by the Spitzer Space Telescope revealed that M31 contains one trillion (1012) stars, more than the number of stars in our own galaxy, which is estimated to be c. 200-400 billion.
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. M31 is so distant it takes about 2.5 million years for light to reach us from there. Much about M31 remains unknown, including how it acquired its unusual double-peaked center.
Credit: Charles Shahar/Caltech/Digital Sky Survey 2
http://www.lightfigures.com/DSS2/
1 comment(s):
Another absolutely stunning image. The definition and colour cannot help but fascinate those who are amateurs in the astronomy world, like myself.
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