A Hubble image of the globular cluster Omega Centauri, a collection of myriad stars colored red, white, and blue on the black background of space.

Hubble Captures Omega Centauri

An international team of astronomers has used more than 500 images from NASA's Hubble Space Telescope – spanning two decades of observations – to detect seven fast-moving stars in the innermost region of the globular star cluster Omega Centauri, the largest and brightest globular cluster in the sky. These stars provide new compelling evidence for the presence of the gravitational pull from an intermediate-mass black hole (IMBH) tugging on them. Only a few other IMBH candidates have been found to date. Omega Centauri is visible from Earth with the naked eye and is one of the favorite celestial objects for stargazers living in the southern hemisphere. Although the cluster is 17,700 light-years away, located just above the plane of the Milky Way, it appears almost as large as the full Moon when seen from a dark rural area. The exact classification of Omega Centauri has evolved through time, as our ability to study it has improved. It was first listed in Ptolemy's catalog nearly 2,000 years ago as a single star. Edmond Halley reported it as a nebula in 1677. In the 1830s the English astronomer John Herschel was the first to recognize it as a globular cluster. Omega Centauri consists of roughly 10 million stars that are gravitationally bound. The cluster is about 10 times as massive as other big globular clusters – almost as massive as a small galaxy.

Credits: ESA/Hubble, NASA, Maximilian Häberle (MPIA)