Messier 39

Messier 39
Open cluster Messier 39 in Cygnus
Observation data (J2000 epoch)
Right ascension21h 31m 48.0s[1]
Declination+48° 26′ 00″[1]
Distance1,010 ly (311 pc)[2]
Apparent magnitude (V)4.6[3]
Apparent dimensions (V)29′[4]
Physical characteristics
Mass232+210
−110[5] M☉
Estimated age278.6[1] Myr
Other designationsM 39, NGC 7092,[6] Cr 438
Associations
ConstellationCygnus
See also: Open cluster, List of open clusters

Messier 39 or M39, also known as NGC 7092, is an open cluster of stars in the constellation of Cygnus, sometimes referred to as the Pyramid Cluster. It is positioned two degrees south of the star Pi Cygni[7] and around 9° east-northeast of Deneb.[8] The cluster was discovered by Guillaume Le Gentil in 1749, then Charles Messier added it to his catalogue in 1764.[7][9] When observed in a small telescope at low power the cluster shows around two dozen members[7] but is best observed with binoculars.[7] It has a total integrated magnitude (brightness) of 4.6 and spans an angular diameter of 29 arcminutes[4] – about the size of the full Moon.[8] It is centered about 1,010 light-years (311 parsecs) away.[2]

This cluster has an estimated mass of 232 M☉ and a linear tidal radius of 8.6±1.8 pc.[5] Of the 15 brightest components, six form binary star systems; one more is suspected. HD 205117 is a probable eclipsing binary system with a period of 113.2 days that varies by 0.051 in visual magnitude. Both members seem to be subgiants.[10] Within are at least five[11] chemically peculiar stars and ten[12] suspected short-period variable stars.

  1. ^ a b c Cite error: The named reference Wu2009 was invoked but never defined (see the help page).
  2. ^ a b Cite error: The named reference kharchenko2005 was invoked but never defined (see the help page).
  3. ^ "Messier 39". SEDS Messier Catalog. Retrieved 29 April 2022.
  4. ^ a b Cite error: The named reference webda2018a was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Piskunov2008 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  7. ^ a b c d Cite error: The named reference Magda2015 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference Bone2005 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Stoyan2008 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Zakirov1995 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Gray2002 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Schuff2006 was invoked but never defined (see the help page).