The multi-color stars of globular cluster NGC 6362

Posted by Thomas Anderson

NASA's Hubble Space Telescope recently captured an impressive view of the center of globular cluster NGC 6362.

The image of this spherical collection of stars takes a closer look at the core of the globular cluster, which boasts a high concentration of stars with different colors.

Tightly bound by gravity, globular clusters are composed of old stars, which, at around 10 billion years old, are much older than the sun. These clusters are fairly common, with more than 150 currently known in our galaxy, the Milky Way, and more which have been spotted in other galaxies.

Globular clusters are among the oldest structures in the Universe that are accessible to direct observational investigation, essentially making them living fossils from the early years of the cosmos.

As such, astronomers are able to infer critical properties of globular clusters by analyzing the light from their constituent stars. For many years, they were regarded as ideal laboratories for testing the standard stellar evolution theory. Among other things, this theory suggests that most of the stars within a globular cluster should be of a similar age.

Recently, however, high precision measurements performed in numerous globular clusters, primarily with the Hubble Space Telescope, have led some to question this widely accepted theory. Specifically, certain stars appear younger and bluer than their companions and have therefore been dubbed blue stragglers. NGC 6362 contains many of these stars.

As they are usually found in the core regions of clusters, where the concentration of stars is large, the most likely explanation for this unexpected population of objects seems to be that they could be either the result of stellar collisions or transfer of material between stars in binary systems. This influx of new material would heat up the star and make it appear younger than its neighbors.

NGC 6362 is located approximately 25 000 light-years from Earth in the constellation of Ara (The Altar). British astronomer James Dunlop first observed this globular cluster on 30 June 1826.