Messier 12

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Messier 12
M12 Adam Block.jpg
Globular cluster Messier 12 in Ophiuchus
Observation data (J2000 epoch)
Class IX [1]
Constellation Ophiuchus
Right ascension 16h 47m 14.18s [2]
Declination –01° 56 54.7 [2]
Distance 16.44 ± 0.16  kly (5.04 ± 0.05  kpc) [3]
Apparent magnitude (V)6.7 [4]
Apparent dimensions (V)16.0
Physical characteristics
Mass8.7×104 [5]   M
Radius37.2 ly [NB 1]
Metallicity  = –1.14 [6] dex
Estimated age13.8 ± 1.1  Gyr [3]
Other designations NGC 6218 [7]
See also: Globular cluster, List of globular clusters

Messier 12 or M 12 (also designated NGC 6218) is a globular cluster in the constellation of Ophiuchus. It was discovered by the French astronomer Charles Messier on May 30, 1764, who described it as a "nebula without stars". [8] In dark conditions this cluster can be faintly seen with a pair of binoculars. Resolving the stellar components requires a telescope with an aperture of 8 in (20 cm) or greater. [9] In a 10 in (25 cm) scope, the granular core shows a diameter of 3 (arcminutes) surrounded by a 10 halo of stars. [8]

Contents

M12 is roughly 3° [9] northwest from the cluster M10 and 5.6° east southeast from star Lambda Ophiuchi. It is also located near the 6th magnitude 12 Ophiuchi. [10] The cluster is about 16,400 light-years (5,000 parsecs) [3] from Earth and has a spatial diameter of about 75 light-years. The brightest stars of M12 are of 12th magnitude. M10 and M12 are only a few thousand light-years away from each other and each cluster would appear at about magnitude 4.5 from the other. [10] With a Shapley-Sawyer rating of IX, [1] it is rather loosely packed for a globular and was once thought to be a tightly concentrated open cluster. Thirteen variable stars have been recorded in this cluster. M12 is approaching us at a velocity of 16 km/s. [11]

A study published in 2006 concluded that this cluster has an unusually low number of low-mass stars. The authors surmise that they were stripped from the cluster by passage through the relatively matter-rich plane of the Milky Way. [12]

See also

Notes

  1. distance × sin( diameter_angle / 2 ) = 37.2 ly radius

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<span class="mw-page-title-main">Messier 69</span> Globular cluster in the constellation Sagittarius

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<span class="mw-page-title-main">NGC 2419</span> Globular cluster in the constellation Lynx

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<span class="mw-page-title-main">NGC 3201</span> Globular cluster in the constellation Vela

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<span class="mw-page-title-main">NGC 288</span> Globular cluster in the constellation Sculptor

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<span class="mw-page-title-main">NGC 6723</span> Globular cluster in the constellation Sagittarius

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<span class="mw-page-title-main">NGC 6752</span> Globular cluster in the constellation Pavo

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<span class="mw-page-title-main">NGC 362</span> Globular cluster located in the constellation Tucana

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<span class="mw-page-title-main">NGC 6352</span> Globular cluster in the constellation Ara

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References

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