Hostile Environment

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A galaxy cluster can be a hostile environment. A galaxy can be harassed, pulled apart, stripped of its ability to give birth to stars, and even absorbed in a hostile takeover.

A team of astronomers is studying these processes in the Coma Cluster, a collection of thousands of galaxies that's about 300 million light-years away. The team is examining pictures taken with an instrument aboard Hubble Space Telescope called the Advanced Camera for Surveys.

One thing the astronomers are interested in is how galaxies are transformed as they fall into the cluster.

There's a difference in the types of galaxies that belong to clusters and those that don't. Outside the clusters, there are lots of spiral galaxies, which have clouds of cold gas that are giving birth to new stars. In the hearts of clusters, though, there are relatively few of these galaxies. Instead, most of the galaxies look featureless and inert, with populations of old stars.

The interaction between the galaxies themselves can contribute to the difference. A close encounter between two galaxies in a cluster can rip out streamers of stars and gas. It may also channel gas from the outer parts of a spiral galaxy into its center, triggering bouts of starbirth. And on rare occasions, two galaxies can merge.

Coma is a densely packed galaxy cluster, so it's fairly easy to study. Examining the cluster should help astronomers learn about these hostile environments.

Script by Damond Benningfield, Copyright 2008

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