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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 ...
Messier 22 or M22, also known as NGC 6656 or the Great Sagittarius Cluster, is an elliptical globular cluster of stars in the constellation Sagittarius, near the Galactic bulge region. It is one of the brightest globulars visible in the night sky.
It is the prototype of a class of anomalous Cepheids which is intermediate in the H-R diagram between the type I classical Cepheids and the type II Cepheids. It varies from magnitude 14.45 to 15.10 over 0.82 days. [3] It is located 4 arcminutes from the centre of (and assumed to be a member star of) the globular cluster NGC 5466.
See also: Globular cluster, List of globular clusters Messier 79 (also known as M79 or NGC 1904 ) is a globular cluster in the southern constellation Lepus . It was discovered by Pierre Méchain in 1780 and is about 42,000 light-years away from Earth and 60,000 light years from the Galactic Center .
See also: Globular cluster, List of globular clusters: Messier 5 or M5 (also designated NGC 5904) is a globular cluster in the constellation Serpens.
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″.
It is an Oosterhoff type II (OoII) globular cluster, which means it belongs to the group of metal-poor clusters with longer period RR Lyrae variable stars. The 1997 Catalogue of Variable Stars in Globular Clusters listed 28 candidate variable stars in the cluster, although only 20 have been confirmed. As of 2001, there are 17 known RR Lyrae ...
At 175 light-years in diameter, it is one of the larger globular clusters known. The cluster is rich, compact, and significantly elliptical. It is 12.5 billion years old and one of the older globular clusters associated with the Milky Way galaxy. [7] M2 contains about 150,000 stars, including 21 known variable stars.