Messier 69
| Messier 69 | |
|---|---|
| Observation data (J2000 epoch) | |
| Class | V |
| Constellation | Sagittarius |
| Right ascension | 18h 31m 23.10s |
| Declination | −32° 20′ 53.1″ |
| Distance | 29 kly (8.8 kpc) |
| Apparent magnitude (V) | 7.6 |
| Apparent dimensions (V) | 10.8′ |
| Physical characteristics | |
| Mass | 2.0×105 M☉ M☉ |
| Radius | 45 ly |
| Tidal radius | 91.9 ly. |
| Metallicity | = –0.78 dex |
| Estimated age | 13.06 Gyr |
| Other designations | GCl 96, M69, NGC 6637,NGC 6634 |
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Messier 69 or M69, also known NGC 6637, and NGC 6634, is a globular cluster in the southern constellation of Sagittarius. It can be found 2.5° to the northeast of the star Epsilon Sagittarii and is dimly visible in 50 mm aperture binoculars. The cluster was discovered by Charles Messier on August 31, 1780, the same night he discovered M70. At the time, he was searching for an object described by Nicolas-Louis de Lacaille in 1751–2 and thought he had rediscovered it, but it is unclear if Lacaille actually described M69.
This cluster is about 28,700 light-years away from Earth and 5,200 ly from the Galactic Center, with a spatial radius of 45 light-years. It is a relatively metal-rich globular cluster that is a likely member of the galactic bulge population. It has a mass of 200000 M☉ with a half-mass radius of 11.6 ly, a core radius of 29.2 ly, and a tidal radius of 91.9 ly. Its center has a bright luminosity density of 6,460 L☉·pc−3 (meaning per cubic parsec). It is a close neighbor of its analog M70 – possibly only 1,800 light-years separates the two.