Messier 75 information

Messier 75
Messier 75
Observation data (J2000 epoch)
Class	I
Constellation	Sagittarius
Right ascension	20h 06m 04.85s
Declination	−21° 55′ 17.85″
Distance	68 kly (20.9 kpc)
Apparent magnitude (V)	8.5
Apparent dimensions (V)	6.8′
Physical characteristics
Absolute magnitude	−8.57
Radius	67 ly
Tidal radius	5.7′
Metallicity	= −1.29 dex
Other designations	GCl 116, M75, NGC 6864
	See also: Globular cluster, List of globular clusters

Messier 75 or M75, also known as NGC 6864, is a giant globular cluster of stars in the southern constellation Sagittarius.^[a] It was discovered by Pierre Méchain in 1780 and included in Charles Messier's catalog of comet-like objects that same year.^[8]

M75 is about 67,500^[3] light years away from Earth and is 14,700^[6] light years away from, and on the opposite side of, the Galactic Center.^[9] 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 −15°±30°.^[3] The absolute magnitude of M75 is about −8.5, equating to 180,000 times more luminous than the Sun (L_☉).^[8]

The cluster has a half-light radius of 9.1 ly (2.80 pc)^[6] with a core radius of about 1.6 ly (0.5 pc) and appears not to have undergone core collapse yet. The mass density at the core is 7.9×10⁴ M_☉·pc⁻³.^[b]^[2] There are 38 RR Lyrae variable stars and the cluster appears to be Oosterhoff-intermediate in terms of metallicity.^[9] 62 candidate blue stragglers have been identified in the cluster field, with 60% being in the core region.^[2]

Messier 75 is part of the Gaia Sausage, the hypothesized remains of a dwarf galaxy that merged with the Milky Way.^[10] 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 57,000 ly (17,500 pc).^[3]

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^ ^a ^b ^c ^d ^e Cite error: The named reference Koch2018 was invoked but never defined (see the help page).
^ "Messier 75". SEDS Messier Catalog. Retrieved 30 April 2022.
^ ^a ^b From trigonometry: radius = distance × sin( diameter_angle / 2 ) = 67 ly.
^ ^a ^b ^c Cite error: The named reference Bergh2012 was invoked but never defined (see the help page).
^ Cite error: The named reference simbad was invoked but never defined (see the help page).
^ ^a ^b Cite error: The named reference Frommert2007 was invoked but never defined (see the help page).
^ ^a ^b Cite error: The named reference Corwin2003 was invoked but never defined (see the help page).
^ Cite error: The named reference Myeong2018 was invoked but never defined (see the help page).

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[4] "Messier 75". SEDS Messier Catalog. Retrieved 30 April 2022.

[trig-5] From trigonometry: radius = distance × sin( diameter_angle / 2 ) = 67 ly.

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[Myeong2018-12] Cite error: The named reference Myeong2018 was invoked but never defined (see the help page).

Messier 75 information

and 27 Related for: Messier 75 information

Messier 75

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Messier object

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Messier 90

M75

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List of most massive star clusters

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Messier 75

Observation data (J2000 epoch)
Class	I^[1]
Constellation	Sagittarius
Right ascension	20^h 06^m 04.85^s^[2]
Declination	−21° 55′ 17.85″^[2]
Distance	68 kly (20.9 kpc)^[3]
Apparent magnitude (V)	8.5^[4]
Apparent dimensions (V)	6.8′
Physical characteristics
Absolute magnitude	−8.57^[2]
Radius	67 ly^[5]
Tidal radius	5.7′^[3]
Metallicity	${\begin{smallmatrix}\left[{\ce {Fe}}/{\ce {H}}\right]\end{smallmatrix}}$ = −1.29^[6] dex
Other designations	GCl 116, M75, NGC 6864^[7]
See also: Globular cluster, List of globular clusters