NGC 1261 (also known as Caldwell 87) is a
globular cluster of stars in the southern
constellation of
Horologium, first discovered by Scottish astronomer
James Dunlop in 1826. The cluster is located at a distance of 53
kilolight-years from the
Sun, and 59 kilolight-years from the
Galactic Center.[3] It is about 10.24[7] billion years old with 341,000[6] times the
mass of the Sun. The cluster does not display the normal indications of
core 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 a
Shapley–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.
^Wehlau, A.; Demers, S. (May 1977), "NGC 1261 and the Oosterhoff type I systems", Astronomy and Astrophysics, 57: 251–256,
Bibcode:
1977A&A....57..251W.