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Why is Omega Centauri an unusual globular cluster?
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Star cluster
Centre of star cluster 47 Tucanae (NGC 104), showing the colours of various stars.
Most of the brightest stars are older yellow stars, but a few young blue stars are also visible. This picture is a composite of three images taken by the Hubble Space Telescope.
Omega Centauri is considered an unusual globular cluster for several distinct reasons:
- Physical Structure: Unlike most globular clusters, which are typically spherical, Omega Centauri is noticeably elliptical in shape. Additionally, it lacks a sharp, highly concentrated nucleus, a feature common to many other clusters like 47 Tucanae.12
- Scale and Brightness: It is the brightest and one of the largest globular clusters, containing several million stars. Its apparent diameter is exceptionally large, measuring about one degree.312
- Potential Central Object: There is evidence suggesting the presence of a black hole at its center, estimated to be 40,000 times as massive as the Sun.3
- Variable Stars: It is the richest cluster in variable stars, with nearly 200 known RR Lyrae variables identified within it.1