A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of member stars. Their name is derived from Latin globulus. Globular clusters are occasionally known simply as "globulars".
The Sagittarius Dwarf Spheroidal Galaxy (Sgr dSph), also known as the Sagittarius Dwarf Elliptical Galaxy, is an elliptical loop-shaped satellite galaxy of the Milky Way. It contains four globular clusters in its main body, with the brightest of them – NGC 6715 (M54) – being known well before the discovery of the galaxy itself in 1994. Sgr dSph is roughly 10,000 light-years in diameter, and is currently about 70,000 light-years from Earth, travelling in a polar orbit at a distance of about 50,000 light-years from the core of the Milky Way. In its looping, spiraling path, it has passed through the plane of the Milky Way several times in the past. In 2018 the Gaia project of the European Space Agency showed that Sgr dSph had caused perturbations in a set of stars near the Milky Way's core, causing unexpected rippling movements of the stars triggered when it moved past the Milky Way between 300 and 900 million years ago.
Messier 2 or M2 is a globular cluster in the constellation Aquarius, five degrees north of the star Beta Aquarii. It was discovered by Jean-Dominique Maraldi in 1746, and is one of the largest known globular clusters.
Messier 56 is a globular cluster in the constellation Lyra. It was discovered by Charles Messier in 1779. It is angularly found about midway between Albireo and Sulafat. In a good night sky it is tricky to find with large (50–80 mm) binoculars, appearing as a slightly fuzzy star. The cluster can be resolved using a telescope with an aperture of 8 in (20 cm) or larger.
A dwarf spheroidal galaxy (dSph) is a term in astronomy applied to small, low-luminosity galaxies with very little dust and an older stellar population. They are found in the Local Group as companions to the Milky Way and to systems that are companions to the Andromeda Galaxy (M31). While similar to dwarf elliptical galaxies in appearance and properties such as little to no gas or dust or recent star formation, they are approximately spheroidal in shape and generally have lower luminosity.
Segue 1 is a dwarf spheroidal galaxy or globular cluster situated in the Leo constellation and discovered in 2006 by Sloan Digital Sky Survey. It is located at a distance of about 23 kpc from the Sun and moves away from the Sun with the velocity of about 206 km/s. Segue 1 has a noticeably elongated shape with the half-light radius of about 30 pc. This elongation may be caused by the tidal forces acting from the Milky Way galaxy if Segue 1 is being tidally disrupted now.
Leo IV is a dwarf spheroidal galaxy situated in the Leo constellation, discovered in 2006 in the data obtained by the Sloan Digital Sky Survey. The galaxy is located at the distance of about 160 kpc from the Sun and moves away from the Sun with the velocity of about 130 km/s. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an approximately round shape with the half-light radius of about 130 pc.
Canes Venatici II or CVn II is a dwarf spheroidal galaxy situated in the Canes Venatici constellation and discovered in 2006 in data obtained by the Sloan Digital Sky Survey. The galaxy is located at a distance of about 150 kpc from the Sun and moves towards the Sun with the velocity of about 130 km/s. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an elliptical shape with a half-light radius of about 74+14
−10 pc.
Coma Berenices or Com is a dwarf spheroidal galaxy situated in the Coma Berenices constellation and discovered in 2006 in data obtained by the Sloan Digital Sky Survey. The galaxy is located at the distance of about 44 kpc from the Sun and moves away from the Sun with the velocity of about 98 km/s. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an elliptical shape with the half-light radius of about 70 pc.
Hercules, or Her, is a dwarf spheroidal galaxy situated in the Hercules constellation and discovered in 2006 in data obtained by the Sloan Digital Sky Survey. The galaxy is located at a distance of about 140 kpc from the Sun and moves away from the Sun with a velocity of about 45 km/s. It is classified as a dwarf spheroidal galaxy (dSph). It has a noticeably elongated shape with a half-light radius of about 350 pc. This elongation may be caused by tidal forces acting from the Milky Way galaxy, meaning that Her is being tidally disrupted now. Her also shows some gradient of velocities across the galaxy's body and is embedded into a faint stellar stream, which also points towards its ongoing tidal disruption.
Segue 3 is a faint star cluster of the Milky Way galaxy discovered in 2010 in the data obtained by Sloan Digital Sky Survey. It is located in the Pegasus constellation at the distance of about 17 kpc from the Sun and moves away from it with the velocity of 167.1 ± 1.5 km/s.
Pisces II is a dwarf spheroidal galaxy situated in the Pisces constellation and discovered in 2010 in the data obtained by the Sloan Digital Sky Survey. The galaxy is located at the distance of about 180 kpc (kiloparsecs) from the Sun. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an elongated shape with the half-light radius of about 60 pc and ratio of the axis of about 5:3.
NGC 5286 is a globular cluster of stars located some 35,900 light years away in the constellation Centaurus. At this distance, the light from the cluster has undergone reddening from interstellar gas and dust equal to E(B – V) = 0.24 magnitude in the UBV photometric system. The cluster lies 4 arc-minutes north of the naked-eye star M Centauri. It was discovered by Scottish astronomer James Dunlop, active in Australia, and listed in his 1827 catalog.
Koposov 1 is a low-luminosity globular cluster in the constellation Virgo in the halo of the Milky Way galaxy. It was discovered, along with globular cluster Koposov 2 by S. Koposov et al. in 2007. Koposov 1 and Koposov 2 were described by their discoverers as the "lowest luminosity globular clusters orbiting the Milky Way," along with AM 4, Palomar 1, and Whiting 1.
Laevens 1 is a faint globular cluster in the constellation Crater that was discovered in 2014. It is also known as Crater, the Crater cluster and PSO J174.0675-10.8774.
The Eridanus II Dwarf is a low-surface brightness dwarf galaxy in the constellation Eridanus. Eridanus II was independently discovered by two groups in 2015, using data from the Dark Energy Survey. This galaxy is probably a distant satellite of the Milky Way. Li et al., 2016. Eridanus II contains a centrally located globular cluster; and is the smallest, least luminous galaxy known to contain a globular cluster. Crnojević et al., 2016. Eridanus II is significant, in a general sense, because the widely accepted Lambda CDM cosmology predicts the existence of many more dwarf galaxies than have yet been observed. The search for just such bodies was one of the motivations for the ongoing Dark Energy Survey observations. Eridanus II has special significance because of its apparently stable globular cluster. The stability of this cluster, near the center of such a small, diffuse, galaxy places constraints on the nature of dark matter. Brandt 2016.
The Gaia Sausage or Gaia Enceladus is the remains of a dwarf galaxy that merged with the Milky Way about 8–11 billion years ago. At least eight globular clusters were added to the Milky Way along with 50 billion solar masses of stars, gas and dark matter. It represents the last major merger of the Milky Way.
Balbinot I is a low-luminosity globular cluster in the constellation of Pegasus. It is located 31.9 kpc away from the Sun, in the Milky Way galactic halo. Its total luminosity is similar to that of the clusters AM 4 and Koposov I, thus being one of the faintest globular clusters known. From Pan-STARRS data, the presence of tidal tails has been suggested.
NGC 7492 is a globular cluster in the constellation Aquarius. It was discovered by the astronomer William Herschel on September 20, 1786. It resides in the outskirts of the Milky Way, about 80,000 light-years away, more than twice the distance between the Sun and the center of the galaxy, and is a benchmark member of the outer galactic halo. The cluster is immersed in, but does not kinematically belong to, the Sagittarius Stream.
