Astronomy Picture of the Day

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

December 13, 1997

The Coma Cluster of Galaxies
Credit: O. Lopez-Cruz and I. K. Shelton (U. Toronto), Kitt Peak National Obs.

Explanation: Almost every object in the above photograph is a galaxy. The Coma Cluster of Galaxies pictured is one of the densest clusters known - it contains thousands of galaxies. Each of these galaxies house billions of stars - just as our own Milky Way Galaxy does. Although nearby when compared to most other clusters, light from the Coma Cluster still takes hundreds of millions of years to reach us. In fact, the Coma Cluster is so big it takes light millions of years just to go from one side to the other! Most galaxies in Coma and other clusters are ellipticals, while most galaxies outside of clusters are spirals. The nature of Coma's X-ray emission is still being investigated.

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
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&: Michigan Tech. U.