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English: 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 Omega Centauri, the largest and brightest globular cluster in the sky. These stars provide compelling new evidence for the presence of an intermediate-mass black hole (IMBH).

Omega Centauri is visible from Earth with the naked eye and is one of the favorite celestial objects for stargazers in the southern hemisphere. Although the cluster is 17,700 light-years away, lying 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. This image shows the central region of the Omega Centauri globular cluster, where the IMBH candidate was found.

ESA/Hubble, NASA, Maximilian Häberle (MPIA)