Messier 75
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Messier 75 or M75, also known as NGC 6864, is a globular cluster of stars in the southern constellation Sagittarius.Template:Efn It was discovered by Pierre Méchain in 1780 and included in Charles Messier's catalog of comet-like objects that same year.[1]
M75 is about 67,500[2] light years away from Earth and is 14,700[3] light years away from, and on the opposite side of, the Galactic Center.[4] Its apparent size on the sky translates to a true radius of 67 light years.[5] M75 is classified as class I, meaning it is one of the more densely concentrated globular clusters known. It shows a slow rotation around an axis that is inclined along a position angle of Script error: No such module "val"..[2] The absolute magnitude of M75 is about −8.5, equating to 180,000 times more luminous than the Sun (Template:Lo).[1]
The cluster has a half-light radius of Script error: No such module "convert".[3] with a core radius of about Script error: No such module "convert". and appears not to have undergone core collapse yet. The mass density at the core is Script error: No such module "val".·pc−3.Template:Efn[6] There are 38 RR Lyrae variable stars and the cluster appears to be Oosterhoff-intermediate in terms of metallicity.[4] 62 candidate blue stragglers have been identified in the cluster field, with 60% being in the core region.[6]
Messier 75 is part of the Gaia Sausage, the hypothesized remains of a dwarf galaxy that merged with the Milky Way.[7] It is a halo object with an orbital period of 0.4 billion years to travel around the galaxy on a very pronounced ellipse, specifically eccentricity of 0.87. The apocenter (maximal distance from Earth) is about Script error: No such module "convert"..[2]
Gallery
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Messier 75 – wide field view
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Map showing location of M75
See also
References and footnotes
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External links
- Messier 75, Galactic Globular Clusters Database page
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