NGC 2360

Last updated
NGC 2360
NGC2360 - SDSS DR14 (panorama).jpg
Observation data (J2000 epoch)
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 designationsCaroline's Cluster, [3] Caldwell 58, Cr 134, Mel 64 [3]
Associations
Constellation Canis Major
See also: Open cluster, List of open clusters
Map showing the location of NGC 2360 NGC 2360 map.png
Map showing the location of NGC 2360

NGC 2360 (also known as Caroline's Cluster [3] or Caldwell 58) is an open cluster in the constellation Canis Major. It was discovered on 26 February 1783 [4] by Caroline 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 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]

Sirius Mirzam M41.jpg
Sirius and M41 (lower right), M50 (upper left), and NGC 2360 (lower left)

Notes

  1. 1 2 "Results for NGC 2360". NGC/IC Project Database. Archived from the original on 2012-05-20. Retrieved 2010-12-03.
  2. 1 2 3 "SEDS Online NGC Database". Results for NGC 2360. Retrieved 2010-12-03.
  3. 1 2 3 "NGC 2360". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2010-12-03.
  4. 1 2 Hoskin, Michael (2005). "Caroline Herschel as observer" (PDF). Journal for the History of Astronomy . 36 (4): 373–406. Bibcode:2005JHA....36..373H. doi:10.1177/002182860503600402. S2CID   118428465.
  5. 1 2 3 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" (PDF). Deepsky Delights. The Astronomical Society of Southern Africa. pp. 234–36. Retrieved 16 March 2014.
  7. Eggen, Olin J. (1968). "The Intermediate-Age Cluster NGC 2360" (PDF). 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" (PDF). Astronomy and Astrophysics. 273 (1): 61–72. Bibcode:1990A&A...237...61M.


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