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Coma Galaxy Cluster

April 19, 2013

The golden tresses of Queen Berenice adorn the sky on spring evenings. They form the constellation Coma Berenices, a spray of stars that’s visible through binoculars high in the east at nightfall.

If you look deep into the constellation, you’ll see that the locks have some beautiful decorations - thousands of galaxies that form the Coma Cluster.

The cluster is only about 300 million light-years away, so its galaxies are fairly easy to observe and study. There’s plenty to see - galaxies that range from little puffs of stars to monsters that are many times larger and more massive than our own galaxy, the Milky Way.

The most impressive member of the Coma Cluster is NGC 4881. It’s a type known as a “cD” galaxy. These galaxies can be up to 50 times wider than the Milky Way. They’re also much more massive than the Milky Way, and they contain many more stars.

A cD galaxy has a bright, dense ball of stars in the middle, but its outskirts are spread pretty thin - you can easily see background galaxies right through it.

Astronomers are still trying to understand how cD galaxies took shape. They may have formed from the mergers of smaller galaxies, and added to their great heft by pulling in the gas that permeates galaxy clusters. They are likely to pull in even more material - adding to their impressive dimensions.

If you have a small telescope, pick out a few of Coma’s galaxies yourself, floating high in the east this evening.


Script by Damond Benningfield, Copyright 2013

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