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The first known globular cluster, now called M 22, was discovered in 1665 by Abraham Ihle, a German amateur astronomer. [4] [5] [6] The cluster Omega Centauri, easily visible in the southern sky with the naked eye, was known to ancient astronomers like Ptolemy as a star, but was reclassified as a nebula by Edmond Halley in 1677, [7] then finally as a globular cluster in the early 19th century ...
Baum used just a single globular cluster, but individual formations are often poor standard candles. Canadian astronomer René Racine assumed the use of the globular cluster luminosity function (GCLF) would lead to a better approximation. The number of globular clusters as a function of magnitude is given by:
Clusters with low metallicity are somewhat larger than metal-rich clusters. [124] In 2014, HVGC-1, the first hypervelocity globular cluster, was discovered escaping from M87 at 2,300 km/s. The escape of the cluster with such a high velocity was speculated to have been the result of a close encounter with, and subsequent gravitational kick from ...
NGC 6397 (also known as Caldwell 86) is a globular cluster in the constellation Ara that was discovered by French astronomer Nicolas-Louis de Lacaille in 1752. [9] It is located about 7,800 light-years from Earth, [3] making it one of the two nearest globular clusters to Earth (the other one being Messier 4).
These are globular clusters within the halo of the Milky Way galaxy. The diameter is in minutes of arc as seen from Earth. For reference, the J2000 epoch celestial coordinates of the Galactic Center are right ascension 17 h 45 m 40.04 s, declination −29° 00′ 28.1″.
Nearest globular cluster to the Earth. Also the first globular cluster known to have exoplanets (PSR B1620-26b) Messier 12: 74.4 [28] Messier 70: 68 [29] NGC 290: 66 [30] Open cluster: Messier 28: 60 [31] Globular cluster: Messier 18: 52.4 [32] Open cluster: The following notable star clusters are listed for the purpose of comparison. MGC1: 49 ...
The observed state of gas within a cluster is determined by a combination of shock heating during accretion, radiative cooling, and thermal feedback triggered by that cooling. The density , temperature , and substructure of the intracluster X-Ray gas therefore represents the entire thermal history of cluster formation.
In surveys of globular clusters, ... making up 9% of observed RR Lyrae, and have shorter periods and more sinusoidal variation ... typically less than one day ...