Messier 69

Messier 69 or M69, also known NGC 6637, and NGC 6634,^[9][10] is a globular cluster in the southern constellation of Sagittarius.^[a] 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.^[11]

Messier 69
Globular cluster Messier 69 by Hubble Space Telescope; 3.5′ view Credit: NASA/STScI/WikiSky
Observation data (J2000 epoch)
Class	V[1]
Constellation	Sagittarius
Right ascension	18h 31m 23.10s[2]
Declination	−32° 20′ 53.1″[2]
Distance	29 kly (8.8 kpc)[3]
Apparent magnitude (V)	7.6[4]
Apparent dimensions (V)	10.8′[3]
Physical characteristics
Mass	2.0×105 M☉[5] M☉
Radius	45 ly[6]
Tidal radius	91.9 ly.[3]
Metallicity	${\displaystyle {\begin{smallmatrix}\left[{\ce {Fe}}/{\ce {H}}\right]\end{smallmatrix}}}$ = –0.78[7] dex
Estimated age	13.06 Gyr[7]
Other designations	GCl 96, M69, NGC 6637,[8]NGC 6634[9]
See also: Globular cluster, List of globular clusters

This cluster is about 28,700^[3] light-years away from Earth and 5,200 ly from the Galactic Center,^[12] with a spatial radius of 45 light-years.^[6] It is a relatively metal-rich globular cluster that is a likely member of the galactic bulge population.^[13] It has a mass of 200000 M_☉ with a half-mass radius of 11.6 ly,^[5] a core radius of 29.2 ly, and a tidal radius of 91.9 ly.^[3] Its center has a bright luminosity density of 6,460 L_☉·pc⁻³ (meaning per cubic parsec).^[12] It is a close neighbor of its analog M70 – possibly only 1,800 light-years separates the two.^[14]

Gallery

• 
  As globular clusters go, M69 is one of the most metal-rich on record.^[15]
• 
  Map showing location of M69

See also

• List of Messier objects