Scintillating Globular Cluster NGC 6540

This scintillating image showcases the globular cluster NGC 6540 in the constellation Sagittarius. A globular cluster is a stable, tightly bound multitude of stars that can contain anywhere from tens of thousands to millions of stars, all trapped in a closely-packed group by their mutual gravitational attraction. The brightest stars in this Hubble Space Telescope image are adorned with prominent cross-shaped patterns of light known as diffraction spikes, caused by their light reflecting off the structure of Hubble rather than the stars themselves. Hubble peered into the heart of NGC 6540 to help astronomers measure the ages, shapes, and structures of globular clusters toward the center of the Milky Way. The gas and dust shrouding the center of our galaxy block some of the light from these clusters, as well as subtly changing the colors of their stars. Globular clusters contain insights into the earliest history of the Milky Way, and studying them can help astronomers understand how our galaxy has evolved.