Globular Star Cluster NGC 6397 in Ara | Hubble Space Telescope

Globular Star Cluster NGC 6397 in Ara | Hubble Space Telescope

This glittering image captures a globular cluster called NGC 6397 (also known as Caldwell 86) that was discovered by French astronomer Nicolas-Louis de Lacaille in 1752. It sits 7,800 light-years away within the Milky Way galaxy, making it one of the closest globular clusters to Earth in the constellation Ara.

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 resulting in a blue color.

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.

Learn more: "How White Dwarfs Get Their ‘Kicks’"
https://science.nasa.gov/missions/hubble/how-white-dwarfs-get-their-kicks/

Credit: NASA, European Space Agency (ESA), and H. Richer (University of British Columbia)
Capture Date: Dec. 4, 2007

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