NGC 6752 (also known asCaldwell 93 and nicknamed theGreat Peacock Globular[7]) is aglobular cluster in theconstellationPavo.[8] It is the fourth-brightest globular cluster in the sky, afterOmega Centauri,47 Tucanae andMessier 22, respectively. It is best seen from June to October in the Southern Hemisphere.[9] It is also known asNGC 6777, though this identification is uncertain.[10][11][12]
NGC 6752 was first identified by oneJames Dunlop of Parramatta on 30 June 1826, who described it as an irregular bright nebula which could be resolved into a cluster of many stars, highly compressed at the centre. This corresponds with a core region densely populated with stars around 1.3light-years in diameter, which indicates it has undergonecore 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] It belongs toShapley–Sawyer Concentration Class VI, namely of intermediate density,[1] and has been calculated to be 11.78 billion years old.[6] There are many binary stars in the system, as well asblue stragglers, which are likely to have been formed by collisions and mergers of smaller stars.
The apparent magnitude of the cluster is 5.4, so it can be seen with the unaided eye.[8] However this depends on good viewing conditions with a minimum of light pollution.[9] With binoculars it can be seen to cover an area three quarters the size of the full moon. It lies 1.5 degrees east of 5th-magnitudeOmega Pavonis.[8] The nearest bright star isPeacock, which lies 3.25 degrees north and 9.25 degrees east.[9]
^abShapley, Harlow; Sawyer, Helen B. (August 1927), "A Classification of Globular Clusters",Harvard College Observatory Bulletin,849 (849):11–14,Bibcode:1927BHarO.849...11S.