Hubble observes a glittering gathering of stars

This glittering gathering of stars is the globular cluster NGC 6558, and it was captured by the NASA/ESA Hubble Space Telescope's Advanced Camera for Surveys. NGC 6558 is closer to the center of the Milky Way than Earth is, and lies about 23,000 light-years away in the constellation Sagittarius.

Globular clusters are tightly bound collections of tens of thousands to millions of stars, and are associated with a wide range of galaxies. NGC 6558 is packed with stars in a rich variety of hues. Some of its brightest inhabitants hold prominent diffraction spikes. These imaging artifacts are the result of starlight interacting with the support system of Hubble's secondary mirror.

Globular clusters are interesting natural laboratories where astronomers can test their theories. Because the stars in a globular cluster formed at approximately the same time with similar initial compositions, they provide unique insights into how different stars evolve under similar conditions. This image comes from a set of observations investigating globular clusters in the inner Milky Way. Astronomers were interested in studying these globular clusters to gain greater insight into how they form and evolve.