ScienceShot: Stars in Cluster Buzzing Past Their Youth

Just like aging hippies, the stars in cluster NGC 3603 won't settle down, astronomers found when they compared images of the cluster taken by the Hubble Space Telescope's Wide Field and Planetary Camera 2 in 2007 with images taken 10 years earlier. NGC 3603, located about 20,000 light-years away in the southern constellation Carina, formed from a giant cloud of gas and dust about 1 million years ago. The full cluster is teeming, with 10,000 stars packed in an area of about 3 light-years square--less than the distance between the sun and its nearest neighbor, Proxima Centauri. Despite the crowding, astronomers had expected NGC 3603's constituent stars to have slowed to a relatively leisurely pace within the cluster. Eventually, they thought, the cluster would settle into a spherical and stable globular cluster. Instead, they report in The Astrophysical Journal Letters, the stars are moving around over twice as fast as expected. Their analyses suggest that astronomers still have some refining to do in their models of how such clusters evolve.