Messier 69

Messier 69
Globular cluster Messier 69 by Hubble Space Telescope; 3.5′ view
Credit: NASA/STScI/WikiSky
Observation data (J2000 epoch)
ClassV[1]
ConstellationSagittarius
Right ascension18h 31m 23.10s[2]
Declination−32° 20′ 53.1″[2]
Distance29 kly (8.8 kpc)[3]
Apparent magnitude (V)7.6[4]
Apparent dimensions (V)10.8′[3]
Physical characteristics
Mass2.0×105 M☉[5] M☉
Radius45 ly[6]
Tidal radius91.9 ly.[3]
Metallicity = –0.78[7] dex
Estimated age13.06 Gyr[7]
Other designationsGCl 96, M69, NGC 6637,[8]NGC 6634[9]
See also: Globular cluster, List of globular clusters

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]

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]

  1. ^ Cite error: The named reference hcob849_11 was invoked but never defined (see the help page).
  2. ^ a b Cite error: The named reference aj140_6_1830 was invoked but never defined (see the help page).
  3. ^ a b c d e Cite error: The named reference Kharchenko2013 was invoked but never defined (see the help page).
  4. ^ "Messier 69". SEDS Messier Catalog. Retrieved April 30, 2022.
  5. ^ a b Cite error: The named reference Mandushev1991 was invoked but never defined (see the help page).
  6. ^ a b From trigonometry: distance × sin( diameter_angle / 2 ) = 28,700 × 0.00157 = 45 ly. radius
  7. ^ a b Cite error: The named reference mnras404_3_1203 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference simbad was invoked but never defined (see the help page).
  9. ^ a b "Your NED Search Results". ned.ipac.caltech.edu. Retrieved August 31, 2024.
  10. ^ "NGC/IC Project Restoration Efforts". ngcicproject.observers.org. Retrieved August 31, 2024.
  11. ^ Cite error: The named reference Thompson2007 was invoked but never defined (see the help page).
  12. ^ a b Cite error: The named reference Piotto2002 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Heasley2000 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Hartmut2011 was invoked but never defined (see the help page).


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