Astronomy Picture of the Day

Discover the cosmos! Each day we feature a different image or photograph of our fascinating universe, along with a brief explanation written by a professional astronomer.

July 24, 1995
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M31: The Andromeda Galaxy
Credit: The Electronic Universe Project

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 2 million years for light to reach us from there.

For more information on M31 see The Electronic Universe Project's write-up.

Many images of Messier objects can be found in The Electronic Universe Project's The Galaxy Gallery: Messier Objects.

Tomorrow's picture: M1: The Crab Nebula

We keep an archive of Astronomy Pictures of the Day.
Astronomy Picture of the Day is created by Robert Nemiroff and Jerry Bonnell who are solely responsible for its content.