"It’s full of stars!" | Globular Star Cluster NGC 6723 in Sagittarius | ESO

"It’s full of stars!" | Globular Star Cluster NGC 6723 in Sagittarius | ESO

A dark background is dotted with countless white and yellow stars in this image, almost like snow falling on a winter’s night. At the center, the density of these dots increases, forming a circular bright white region where the background is almost completely obscured. This dense region is the globular cluster.

This image taken with the European Southern Observatory’s Visible and Infrared Survey Telescope (VISTA) at Paranal Observatory in Chile—might look like a scene from a snowy winter's night, but it’s not. It is an infrared image of NGC 6723, a globular cluster located about 28,000 light years from Earth in the constellation Sagittarius. Globular clusters are spherical-shaped groups of stars, tightly bound together by gravity. Their name is derived from the Latin word globulus, meaning small sphere—somewhat misleading given that NGC 6723, as most globular clusters, contains hundred of thousands to millions of stars.

So far, astronomers have found more than 150 globular clusters in our galaxy, the Milky Way, with most of them estimated to be at least 10 billion years old and hosting some of the oldest stars in the galaxy.

Globular clusters were key to pinpointing our own location within the Milky Way in the early 20th century. American astronomer Harlow Shapley measured the distances to several globular clusters, and noticed that they were arranged in a roughly spherical distribution, but the Sun was not at its center. He correctly inferred that the heart of the Milky Way lays at the center of this distribution of globular clusters, placing the Sun in the suburbs of the galaxy.

Credit: European Southern Observatory (ESO)/S. Meingast et al.

Release Date: Aug. 14, 2023

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