Messier 39 | |
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Observation data (J2000 epoch) | |
Right ascension | 21h31m 48.0s[1] |
Declination | +48° 26′ 00″[1] |
Distance | 1,010 ly (311 pc)[2] |
Apparent magnitude (V) | 4.6[3] |
Apparent dimensions (V) | 29′[4] |
Physical characteristics | |
Mass | 232+210 −110[5] M☉ |
Estimated age | 278.6[1] Myr |
Other designations | M 39, NGC 7092,[6] Cr 438 |
Associations | |
Constellation | Cygnus |
See also: Open cluster, List of open clusters |
Messier 39orM39, also known as NGC 7092, is an open cluster of stars in the constellationofCygnus, positioned two degrees to the 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 5.5 and spans an angular diameterof29 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 radiusof8.6±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.
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