Messier 70

Messier 70
Globular cluster Messier 70 by Hubble Space Telescope; 3.3′ view
Observation data (J2000 epoch)
ClassV[1]
ConstellationSagittarius
Right ascension18h 43m 12.76s[2]
Declination–32° 17′ 31.6″[3]
Distance29.4 kly (9.0 kpc)[4]
Apparent magnitude (V)7.9[5]
Apparent dimensions (V)8.0′[6]
Physical characteristics
Mass1.79×105[4] M☉
Radius34 ly[7]
Tidal radius11.2′[8]
Metallicity = –1.35[9] dex
Estimated age12.80 Gyr[9]
Other designationsGCl 101, M70, NGC 6681[3]
See also: Globular cluster, List of globular clusters

Messier 70 or M70, also known as NGC 6681, is a globular cluster of stars to be found in the south of Sagittarius.[a] It was discovered by Charles Messier in 1780.[b][6] The famous comet Hale–Bopp was discovered near this cluster in 1995.[10][c]

It is about 29,400[4] light years away from Earth and around 6,500 light-years[11] from the Galactic Center. It is roughly the same size and luminosity as its neighbour in space, M69.[12] M70 has a very small core radius of 0.22 ly (0.068 pc)[13] and a half-light radius of 182.0 ly (55.80 pc).[14] This cluster has undergone core collapse, leaving it centrally concentrated[15] with the luminosity distribution following a power law.[11]

There are two distinct stellar populations in the cluster, with each displaying unique abundances. These likely represent different generations of stars.[16] Five known variable stars lie within the broadest radius, the tidal radius, of it, all of which are RR Lyrae variables.[8][17] The cluster may have two blue stragglers near the core.[11]

  1. ^ Cite error: The named reference hcob849_11 was invoked but never defined (see the help page).
  2. ^ Cite error: The named reference aj140_6_1830 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference simbad was invoked but never defined (see the help page).
  4. ^ a b c Cite error: The named reference apj742_1_51 was invoked but never defined (see the help page).
  5. ^ "Messier 70". SEDS Messier Catalog. Retrieved 30 April 2022.
  6. ^ a b Cite error: The named reference Adam2018 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference sma was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference Liller1983 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference mnras404_3_1203 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Mobberley2013 was invoked but never defined (see the help page).
  11. ^ a b c Cite error: The named reference Watson1994 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Hartmut2011 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Djorgovski1993 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Forbes2008 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Pryor1989 was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference OMalley2017 was invoked but never defined (see the help page).
  17. ^ Cite error: The named reference Clement2001 was invoked but never defined (see the help page).


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