Globular Star Cluster NGC 6397 in Ara | Hubble

Globular Star Cluster NGC 6397 in Ara | Hubble

This Hubble Space Telescope view of the core of one of the nearest globular star clusters, called NGC 6397 (also known as Caldwell 86), resembles a treasure chest of glittering jewels. The cluster is located 7,800 light-years away in the constellation Ara within the Milky Way galaxy. Here, the stars are jam-packed together. 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. NGC 6397 was discovered by French astronomer Nicolas-Louis de Lacaille in 1752.

This ancient stellar jewelry box glitters with the light from hundreds of thousands of stars. The cluster’s blue stars are near the end of their lives. These stars have used up their hydrogen fuel that makes them shine. Now they are converting helium to energy in their cores. This fuses at a higher temperature and appears blue. The reddish glow is from red giant stars that have consumed their hydrogen fuel and have expanded in size. The myriad small white objects include stars like our Sun.

Credit: NASA/ESA and the Hubble Heritage Team (AURA/STScI)

Release Date: Aug. 7, 2003

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