| NGC 2360 | |
|---|---|
.jpg) | |
| Observation data (J2000epoch) | |
| Right ascension | 07h 17m 43s[1] |
| Declination | −15° 38′ 29″[1] |
| Apparent magnitude (V) | 7.2[2] |
| Apparent dimensions (V) | 13′[2] |
| Physical characteristics | |
| Other designations | Caroline's Cluster,[3]Caldwell 58,Cr 134,Mel 64[3] |
| Associations | |
| Constellation | Canis Major |
| See also:Open cluster,List of open clusters | |
NGC 2360 (also known asCaroline's Cluster[3] orCaldwell 58) is anopen cluster in theconstellationCanis Major. It was discovered on 26 February 1783[4] byCaroline Herschel, who described it as a "beautiful cluster of pretty compressed stars near 1/2 degree in diameter".[5] Her notes were overlooked until her brotherWilliam included the cluster in his 1786 catalogue of 1000 clusters and nebulae and acknowledged her as the discoverer.[4] The cluster lies 3.5 degrees east ofGamma Canis Majoris and less than one degree northwest of theeclipsing binary starR Canis Majoris; it has a combinedapparent magnitude of 7.2.[5] It is 13 arc minutes in diameter.[2] By the western edge of the cluster is the unrelated star, 5.5-magnitudeHD 56405.[6]
American astronomerOlin J. Eggen surveyed the cluster in 1968, concluding that the brightest star in the field, magnitude-8.96HD 56847, is likely to lie in the field and not a true member of the cluster. He also identified one or possibly twoblue stragglers.[7] These are unexpectedly hot and luminous stars that appear younger than surrounding stars, and have likely developed by sucking matter off companion stars.[8] Four are now recognised to be in the cluster.[9] By analysing the masses of the smallest stars that have evolved intored giants—namely, stars of 1.8 or 1.9 solar masses—Swiss astronomers Jean-Claude Mermilliod andMichel Mayor were able to date the age of the cluster at 2.2 billion years.[10] The cluster has a diameter of around 15 light-years and is located 3700 light-years from Earth.[5]
 Sirius andM41 (lower right),M50 (upper left), and NGC 2360 (lower left) |
