images

Stars in globular cluster NGC 6397 in Ara

by

Nasa/Hubble heritage team/Novapix

Reference

a-agb63-97002

Date

2006-05-08

This Hubble Space Telescope view of the core of one of the nearest globular star clusters, called NGC 6397, located 8,200 light-years away in the constellation Ara. The stellar density is about a million times greater than in our Sun's stellar neighborhood. The stars are only a few light-weeks apart, while the nearest star to our Sun is over four light-years away. The ancient stars are so crowded together that a few of them inevitably collide with each other once in a while. Near misses are even more common. Even so, collisions only occur every few million years or so. When direct collisions occur, the two stars may merge to form a new star called a "blue straggler"; these hot, bright, young stars stand out among the old stars that make up the vast majority of stars in a globular cluster. Several such bright blue stars are visible near the center of the cluster in the image.  This Hubble image is a mosaic of two sets of images taken several years apart by the Wide Field Planetary Camera 2 taken in 1997 and 1999.