NGC 2360

NGC 2360
Observation data (J2000 epoch)
Constellation Canis Major
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 Cl Melotte 64,[3] Caldwell 58, Carolines's Cluster[3]

NGC 2360, also known as Caroline's Cluster,[3] is an open cluster in the constellation Canis Major. It was discovered on 26 February 1783,[4] by Caroline Herschel who wrote, "A beautiful cluster of pretty compressed stars near 1/2 degree in diameter."[5] Her notes were overlooked until her brother William 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 of Gamma Canis Majoris and less than one degree northwest of the eclipsing binary star R Canis Majoris; it has a combined apparent 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-magnitude HD 56405.[6]

American astronomer Olin J. Eggen surveyed the cluster in 1968, concluding that the brightest star in the field, magnitude-8.96 HD 56847, is likely to lie in the field and not a true member of the cluster. He also identified one or possibly two blue 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 into red giants—namely, stars of 1.8 or 1.9 solar masses—Swiss astronomers Jean-Claude Mermilliod and Michel 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]

Notes

  1. ↑ 1.0 1.1 "NGC/IC Project Database". Results for NGC 2360. Retrieved 2010-12-03.
  2. ↑ 2.0 2.1 2.2 "SEDS Online NGC Database". Results for NGC 2360. Retrieved 2010-12-03.
  3. ↑ 3.0 3.1 3.2 "SIMBAD Astronomical Database". Results for NGC 2360. Retrieved 2010-12-03.
  4. ↑ 4.0 4.1 Hoskin, Michael (2005). "Caroline Herschel as observer". Journal for the History of Astronomy 36 (4): 373–406. Bibcode:2005JHA....36..373H.
  5. ↑ 5.0 5.1 5.2 O'Meara, Stephen James (2002). The Caldwell Objects. Cambridge University Press. pp. 231–33. ISBN 978-0-521-82796-6.
  6. ↑ Streicher, Magda (April 2006). "Caroline Herschel’s Deepsky Discoveries". Deepsky Delights. The Astronomical Society of Southern Africa. pp. 234–36. Retrieved 16 March 2014.
  7. ↑ Eggen, Olin J. "The Intermediate-Age Cluster NGC 2360". The Astrophysical Journal 152: 83–87. Bibcode:1968ApJ...152...83E. doi:10.1086/149526.
  8. ↑ Fellman, Megan (17 October 2011). "Astronomers Explain 'Blue Stragglers'". News. Evanston, Illinois: Northwestern University. Retrieved 18 March 2014.
  9. ↑ Ahumada, J. A.; Lapasset, E. (2007). "New catalogue of blue stragglers in open clusters". Astronomy and Astrophysics 463 (2): 789–97. Bibcode:2007A&A...463..789A. doi:10.1051/0004-6361:20054590.
  10. ↑ Mermilliod, Jean-Claude; Mayor, Michel (1990). "Red Giants in Open Clusters. III - Binarity and Stellar Evolution in Five Intermediate-age Clusters: NGC 2360, 2423, 5822, 6811, and IC 4756". Astronomy and Astrophysics 273 (1): 61–72. Bibcode:1990A&A...237...61M.

External links

Coordinates: 07h 17m 42s, −15° 38′ 00″