Chandra offers a look inside stellar cluster NGC 6231

By Brooks Hays  |  May 3, 2018 at 10:16 AM
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May 3 (UPI) -- By studying stellar clusters, astronomers believe they can come to better understand the origin of the sun and sun-like stars. The Chandra X-ray Observatory is helping scientists do just that.

This week, Chandra published new images from its latest stellar cluster survey. The X-ray images showcase NGC 6231, a stellar cluster found 5,200 light years from Earth. NGC 6231 is believed to be between 2 and 7 million years old -- relatively young.

The sun is 4.6 billion years old. But like the stars in NGC 6231, the sun was once part of a large family of stars formed from the same cloud of gas and dust. The cluster that yielded the sun, however, dispersed a long time ago.

Stellar formation in NGC 6231 has only recently stopped, which means astronomers are looking at a cluster in a critical -- and little understood -- stage of its evolution.

Because NGC 6231 lies in the same plane as a crowded band of the Milky Way, studying its stars is not easy. Bright stars behind and in front of the cluster drown out the light of its many sun-like inhabitants.

However, being young, NGC 6231 hosts plenty of youthful stars with unique properties. Young, hot stars burn intensely enough to superheat their outer atmospheres, causing them to emit significant amounts of X-rays -- X-rays Chandra can detect from several thousand light-years away.

By surveying the region's X-ray emissions, Chandra was able to offer scientists a closeup of the cluster's inner region. Astronomers combined Chandra's data with observations by the Visible and Infrared Survey Telescope for Astronomy, or VISTA telescope, to amass the most complete census of NGC 6231 stars yet.

By studying the diversity of properties of stars found within the large cluster and by comparing those properties to stars in other clusters, astronomers can begin to piece together a model of stellar cluster evolution.

NGC 6231 offers a snapshot of an important stage in cluster evolution, when its stellar population has begun to expand and spread out, but before its stars have broken free of the gravity that holds them together.

Chandra's images helped scientists produce a pair of scientific papers detailing NGC 6231.

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