A Tour of NGC 6231

Narrator (April Jubett, CXC): In some ways, star clusters are like giant families with thousands of stellar siblings. These stars come from the same origins — a common cloud of gas and dust — and are bound to one another by gravity. Astronomers think that our Sun was born in a star cluster about 4.6 billion years ago that quickly dispersed.

By studying young star clusters, astronomers hope to learn more about how stars — including our Sun — are born. NGC 6231, located about 5,200 light years from Earth, is an ideal testbed for studying a stellar cluster at a critical stage of its evolution: not long after star formation has stopped.

The discovery of NGC 6231 is attributed to Giovanni Battista Hodierna, an Italian mathematician and priest who published observations of the cluster in 1654. Sky watchers today can find the star cluster to the southwest of the tail of the constellation Scorpius.

NASA's Chandra X-ray Observatory has been used to identify the young Sun-like stars in NGC 6231, which have, until recently, been hiding in plain sight. Young star clusters like NGC 6231 are found in the band of the Milky Way on the sky. As a result, interloping stars lying in front of or behind NGC 6231 greatly outnumber the stars in the cluster. These stars will generally be much older than those in NGC 6231, so members of the cluster can be identified by selecting signs of stellar youth. The Chandra data, combined with infrared data from the VISTA telescope, have provided the best census of young stars in NGC 6231 available.

By studying this cluster and others like it, astronomers hope to better understand our Sun's origins and our shared cosmic ancestry with stars across the Galaxy.