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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 ...
The cluster contains around 400,000 stars, [8] and can be seen with the naked eye under good observing conditions. [10] NGC 6397 is one of at least 20 globular clusters of the Milky Way Galaxy that have undergone a core collapse, [8] meaning that the core has contracted to a very dense stellar agglomeration.
Messier 15 or M15 (also designated NGC 7078 and sometimes known as the Great Pegasus Cluster) is a globular cluster in the constellation Pegasus. It was discovered by Jean-Dominique Maraldi in 1746 and included in Charles Messier 's catalogue of comet -like objects in 1764.
NGC 6355 is a globular cluster located in the constellation Ophiuchus. [5] It is at a distance of 28,000 light years away from Earth, and is currently part of the Galactic bulge. [3] NGC was discovered by the German-born British astronomer William Herschel on 24 May 1784. [6]
This corresponds with a core region densely populated with stars around 1.3 light-years in diameter, which indicates it has undergone core collapse. The cluster lies around 13,000 light-years distant and is one of the closer globular clusters to Earth. It also lies 17,000 light-years away from the galactic centre. [8]
During cloud collapse dozens to tens of thousands of stars form more or less simultaneously which is observable in so-called embedded clusters. The end product of a core collapse is an open cluster of stars. [18] ALMA observations of the Orion Nebula complex provide insights into explosions at star birth. [19]
Core collapse can refer to: The collapse of the stellar core of a massive star, such as the core collapse that produces a supernova Core collapse (cluster) , the dynamic process that leads to a concentration of stars at the core of a globular cluster
It is considered a metal-poor inner halo cluster, being the third most metal-poor globular cluster within 9.8 kly (3 kpc) of the center. [8] The cluster has 5.72 × 10 5 times the mass of the Sun. [5] It is estimated to be around 12.9 billion years old, [6] and is believed to have undergone core collapse. [8]