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 7.9×104M☉·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]
^Shapley, Harlow; Sawyer, Helen B. (August 1927), "A Classification of Globular Clusters", Harvard College Observatory Bulletin, 849 (849): 11–14, Bibcode:1927BHarO.849...11S.
^ abFrommert, Hartmut; Kronberg, Christine (2 September 2007), "Messier 75", SEDS Messier pages, Students for the Exploration and Development of Space (SEDS), retrieved 5 December 2018.
^In a mildly south part of this zone of the sky, +90 declination would give a zenith above the north pole, whereas minus 22 degrees (rounded) precludes it from rising therefore (being above the horizon) at the 68th parallel north and hampers visibility at lower latitudes nearby