Omega Centauri

Omega Centauri (ω Cen, NGC 5139, or Caldwell 80) is a globular cluster in the constellation of Centaurus that was first identified as a non-stellar object by Edmond Halley in 1677. Located at a distance of 17,090 light-years (5,240 parsecs), it is the largest-known globular cluster in the Milky Way at a diameter of roughly 150 light-years. It is estimated to contain approximately 10 million stars, and a total mass equivalent to 4 million solar masses, making it the most massive-known globular cluster in the Milky Way.

Omega Centauri
The globular cluster Omega Centauri
Observation data (J2000 epoch)
Class	VIII
Constellation	Centaurus
Right ascension	13h 26m 47.28s
Declination	−47° 28′ 46.1″
Distance	15.8 ± 1.1 kly (4.84 ± 0.34 kpc)
Apparent magnitude (V)	3.9
Apparent dimensions (V)	36′.3
Physical characteristics
Mass	(4.05±0.1)×106 M☉
Radius	86 ± 6 ly
Metallicity	${\displaystyle {\begin{smallmatrix}\left[{\ce {Fe}}/{\ce {H}}\right]\end{smallmatrix}}}$ = –1.35 dex
Estimated age	11.52 Gyr
Other designations	NGC 5139, GCl 24, ω Centauri, Caldwell 80, Mel 118

Omega Centauri is very different from most other galactic globular clusters to the extent that it is thought to have originated as the core remnant of a disrupted dwarf galaxy.