NGC 1261 (also known asCaldwell 87) is aglobular cluster of stars in the southernconstellation ofHorologium, first discovered by Scottish astronomerJames Dunlop in 1826. The cluster is located at a distance of 53kilolight-years from theSun, and 59 kilolight-years from theGalactic Center.[3] It is about 10.24[7] billion years old with 341,000[6] times themass of the Sun. The cluster does not display the normal indications ofcore collapse, but evidence suggests it may have instead passed through a post core-collapse bounce state within the past two billion years. The central luminosity density is 2.22 L☉·pc−3, which is low for a globular cluster.[8] Despite this, it has aShapley–Sawyer Concentration Class of II,[1] indicating a dense central concentration.
^abShapley, Harlow; Sawyer, Helen B. (August 1927), "A Classification of Globular Clusters",Harvard College Observatory Bulletin,849 (849):11–14,Bibcode:1927BHarO.849...11S.
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