Open Cluster NGC 2539
History
The open cluster NGC 2539 was discovered by William Herschel on 31 January 1785 using his reflecting telescope of 18.7 inch aperture and 20 feet focal length. He listed it as VII 11 with the notes: «A considerably rich cluster of coarsely scattered stars above 20' diameter.» [463]
John Herschel, observing from the Cape of Good Hope on 14 February 1836 listed the cluster NGC 2539 as h 3114 and noted: «A large, extended, rich cluster. Fills field; stars 12 magnitudes ±; a bright star (6 magnitudes) south following.» Later that year on 11 December 1836 he came across that patch in the sky again and listed with h 3115 (NGC 2542) «a fine nebulous star 6 magnitudes, in the following part of the cluster VII 11, and almost unconnected with it. The nebula is faint, but I feel confident that it is not the nebulous haze. [Notandum. — Nothing more difficult than to prove a nebulous star of the 6th mag and above.]» [11] There's no nebulosity around 19 Puppis. Herschel probably was mislead by scattered light or some of the nearby fainter stars.
Physical Properties
| Name | RA | Dec | Type | bMag | vMag | Dim | MD | Dreyer Description | Identification, Remarks |
|---|---|---|---|---|---|---|---|---|---|
| NGC 2539 | 08 10 36.9 | -12 49 14 | OCL (II1m) | 6.5 | 15 | 1.363 | Cl, vL, Ri, lC, st 11…13 | WH VII 11; h 3114; GC 1630; OCL 611 | |
| NGC 2542 | 08 11 16.2 | -12 55 35 | * | 4.7 | Nebulous * 5th mag | h 3115; GC 1632; 19 Pup |
Finder Chart
The open cluster NGC 2539 is located in the constellation Puppis. On 21 January it in opposition with the Sun and is therefore highest in the sky at local midnight.
