A globular cluster is a spheroidal conglomeration of stars that is 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, all orbiting in a stable, compact formation. Globular clusters are similar in form to dwarf spheroidal galaxies, and the distinction between the two is not always clear. Their name is derived from Latin globulus. Globular clusters are occasionally known simply as "globulars".
Star clusters are large groups of stars held together by self-gravitation. Two main types of star clusters can be distinguished: globular clusters are tight groups of ten thousand to millions of old stars which are gravitationally bound, while open clusters are more loosely clustered groups of stars, generally containing fewer than a few hundred members, and are often very young. Open clusters become disrupted over time by the gravitational influence of giant molecular clouds as they move through the galaxy, but cluster members will continue to move in broadly the same direction through space even though they are no longer gravitationally bound; they are then known as a stellar association, sometimes also referred to as a moving group.
Messier 107 or M107, also known as NGC 6171 or the Crucifix Cluster, is a very loose globular cluster in a very mildly southern part of the sky close to the equator in Ophiuchus, and is the last such object in the Messier Catalogue.
Hans-Emil Schuster is a German astronomer and a discoverer of minor planets and comets, who retired in October 1991. He worked at Hamburg Observatory at Bergedorf and European Southern Observatory (ESO), and was former acting director of La Silla Observatory. From 1982 he was married to Rosemarie Schuster née von Holt
Messier 12 or M 12 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". 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. In a 10 in (25 cm) scope, the granular core shows a diameter of 3′ (arcminutes) surrounded by a 10′ halo of stars.
47 Tucanae or 47 Tuc is a globular cluster located in the constellation Tucana. It is about 4.45 ± 0.01 kpc (15,000 ± 33 ly) from Earth, and 120 light years in diameter. 47 Tuc can be seen with the naked eye, with an apparent magnitude of 4.1. It appears about 44 arcminutes across including its far outreaches. Due to its far southern location, 18° from the south celestial pole, it was not catalogued by European astronomers until the 1750s, when the cluster was first identified by Nicolas-Louis de Lacaille from South Africa.
NGC 1850 is a double cluster and a super star cluster in the Dorado constellation, located in the northwest part of the bar of the Large Magellanic Cloud, at a distance of 168 kly (51.5 kpc) from the Sun. It was discovered by Scottish astronomer James Dunlop in 1826.
NGC 3201 is a low galactic latitude globular cluster in the southern constellation of Vela. It has a very low central concentration of stars. This cluster was discovered by James Dunlop on May 28, 1826 and listed in his 1827 catalogue. He described it as "a pretty large pretty bright round nebula, 4′ or 5′ diameter, very gradually condensed towards the centre, easily resolved into stars; the figure is rather irregular, and the stars are considerably scattered on the south".
NGC 5986 is a globular cluster of stars in the southern constellation of Lupus, located at a distance of approximately 34 kilolight-years from the Sun. It was discovered by Scottish astronomer James Dunlop on May 10, 1826. John L. E. Dreyer described it as, "a remarkable object, a globular cluster, very bright, large, round, very gradually brighter middle, stars of 13th to 15th magnitude". Its prograde–retrograde orbit through the Milky Way galaxy is considered irregular and highly eccentric. It has a mean heliocentric radial velocity of +100 km/s. The galacto-centric distance is 17 kly (5.2 kpc), which puts it in the galaxy's inner halo.
NGC 6752 is a globular cluster in the constellation Pavo. It is the fourth-brightest globular cluster in the sky, after Omega Centauri, 47 Tucanae and Messier 22, respectively. It is best seen from June to October in the Southern Hemisphere.
The MPG/ESO telescope is a 2.2-metre f/8.0 (17.6-metre) ground-based telescope at the European Southern Observatory (ESO) in La Silla, Chile. It was built by Zeiss and has been operating since 1984. It was on indefinite loan to the European Southern Observatory from the Max Planck Institute for Astronomy (MPIA). In October 2013 it was returned to the MPIA. Telescope time is shared between MPIA and MPE observing programmes, while the operation and maintenance of the telescope are ESO's responsibility.
Arp-Madore 1 is a globular cluster visible in the constellation Horologium, located 123.3 kiloparsecs away from Earth. It is one of the most distant known globular clusters of the Milky Way galaxy's halo; its distance gives it interest as a test case for gravitational theories. AM 1 has a visual magnitude of 15.07.
NGC 6362 is a globular cluster in the constellation Ara, lying close to Apus in the southern sky. A telescope with a 150mm primary mirror is required to resolve the stars within this irregularly shaped cluster. British astronomer James Dunlop first observed the cluster on 30 June 1826. It is located about 25,000 light-years from Earth and contains a number of blue stragglers.
NGC 2100 is an open cluster in the Large Magellanic Cloud, a small satellite galaxy of the Milky Way. These clusters have a lifespan measured in tens or hundreds of millions of years, as they eventually disperse through gravitational interaction with other bodies. As its format is approximately round, it is sometimes mistaken as a globular cluster.
Dark globular cluster is a proposed type of globular star clusters that has an unusually high mass for the number of stars within it. Proposed in 2015 on the basis of observational data, dark globular clusters are believed to be populated by objects with significant dark matter components, such as central massive black holes.
ESO 444-46 is a class E4 supergiant elliptical galaxy; the dominant and brightest member of the Abell 3558 galaxy cluster around 640 million light-years away in the constellation Centaurus. It lies within the core of the massive Shapley Supercluster, one of the closest neighboring superclusters. It is one of the largest galaxies in the local universe, and possibly contains one of the most massive black holes known. The black hole's mass is very uncertain, with estimates ranging from as low as 501 million M☉, to as high as 77.6 billion M☉.
NGC 1380 is a lenticular galaxy located in the constellation Fornax. It is located at a distance of circa 60 million light years from Earth, which, given its apparent dimensions, means that NGC 1380 is about 85,000 light years across. It was discovered by James Dunlop on September 2, 1826. It is a member of the Fornax Cluster.
NGC 3585 is an elliptical or a lenticular galaxy located in the constellation Hydra. It is located at a distance of circa 60 million light-years from Earth, which, given its apparent dimensions, means that NGC 3585 is about 80,000 light years across. It was discovered by William Herschel on December 9, 1784.
Dante Minniti is an astronomer born in Santa Fe, Argentina on December 1, 1962. He has devoted his career to the study of stellar populations, stellar evolution, globular clusters, galaxy formation, gravitational microlensing, exoplanets and astrobiology. He has been member of the SuperMACHO Team since 2001 and leader of the VVV Survey along with Phil Lucas since 2006 and of its extended version, the VVVX Survey. He has also fostered new scientists, supervising 14 PhD students, 11 Master Students and 17 Postdocs. He is Full Professor and Director of the Astronomy Institute at Andrés Bello National University (UNAB), Chile.
