Jewel Box (star cluster)

From Wikipedia, the free encyclopedia
Jump to: navigation, search
This article is about article is about the star cluster. For other uses, see Jewel box.
Jewel Box
A Snapshot of the Jewel Box cluster with the ESO VLT.jpg
NGC 4755 taken by the VLT
Credit: ESO
Observation data (J2000 epoch)
Constellation Crux
Right ascension 12h 53m 42s[1]
Declination -60° 22.0′[1]
Distance 6.4 kly[2] (1.98 kpc)
Physical characteristics
Mass - M☉
Radius -
Estimated age 14±2Myr[3]
Notable features -
Other designations

NGC 4755,[1] Herschel's Jewel Box,[1]

Kappa Crucis Cluster[1]

See also: Open cluster, List of open clusters

The Jewel Box (also known as NGC 4755, the Kappa Crucis Cluster and Caldwell 94) is an open cluster in the constellation of Crux. As Kappa Crucis, it has a Bayer designation despite the fact that it is a cluster rather than an individual star.

It is one of the finest open clusters discovered by Nicolas Louis de Lacaille when he was in South Africa during 1751–1752. This cluster is one of the youngest known, with an estimated age of only 14 million years. It has an apparent magnitude of 4.2, and is located 6,440 light years from Earth and contains around 100 stars.

This famous group of young bright stars was named the Jewel Box from its description by Sir John Herschel as "a casket of variously coloured precious stones," which refers to its appearance in the telescope. The brightest star is Kappa Crucis, a blue supergiant (HIP 62931, HD 111973, HR 4890). Spectral Type: B3Iae. It shines at an apparent visual magnitude of 5.89. (The cluster looks like a star to the unaided eye and appears close to the easternmost star of the Southern Cross, (Beta Crucis), so is only visible from southern latitudes.

Another cluster, NGC 457, has also a jewel-box-like appearance and lies virtually diametrally opposite this one in the sky in the constellation Cassiopeia.

Contents

Discovery and observation [edit]

The Jewel Box cluster was discovered by Nicolas Louis de Lacaille when he was in the Southern Hemisphere from 1751 to 1753. He saw the object as a nebulous cluster due to the small aperture of his telescope, but was the first to recognize it as consisting of multiple stars.[4] The name "Jewel Box" comes from John Herschel's description of it:

"this cluster, though neither a large nor a rich one, is yet and extremely brilliant and beautiful object when viewed through an instrument of sufficient aperture to show distinctly the very different colour of its constituent stars, which give it the effect of a superb piece of fancy jewellery"
—John Herschel, [4]

Herschel recorded the positions of 100 members of the cluster in 1834–1838.[5]

Physical characteristics [edit]

The Jewel Box cluster is one of the youngest known open clusters.[6]

The mean radial velocity of the Jewel Box cluster is −17.9 kilometres per second (−11.1 mi/s).[7]

The brightest stars in the Jewel Box cluster are supergiants, and include some of the brightest stars in the Milky Way galaxy.[8]

Calculating its distance is difficult due to the proximity of the Coalsack Nebula, which obscures some of its light.[9]

Observation [edit]

The Jewel Box cluster is regarded as one of the finest objects in the southern sky.[10][11] It is visible to the naked eye as a hazy object of the fourth magnitude.[12] The Jewel Box cluster can be easily located using the star Beta Crucis as a guide, and appears as a fourth magnitude object.[13] The three brightest members of the cluster lie in a straight line known as the 'traffic lights' due to their varying colours.[11]

The Jewel Box cluster is impressive when viewed with binoculars[11] or a small telescope, but even more so in a large telescope because the background nebulosity becomes more prominent.[9]

Gallery [edit]

  • Wide Field Image of the Jewel Box.

  • Digitized Sky Survey 2 image of the Jewel Box.

  • Hubble image of the Jewel Box.

  • Putting the images in perspective.

References [edit]

  1. ^ a b c d e "SIMBAD Astronomical Database". Results for NGC 4755. Retrieved 2006-12-14. 
  2. ^ "WEBDA Open cluster". Results for NGC 4755. Retrieved 2007-01-12. 
  3. ^ Bonatto, C; E Bica, S Ortolani, B Barbuy (July 2006). "Detection of K_s-excess stars in the 14 Myr open cluster NGC 4755.". Astronomy & Astrophysics 453: 121–132. arXiv:astro-ph/0603394. Bibcode:2006A&A...453..121B. doi:10.1051/0004-6361:20054620. 
  4. ^ a b O'Meara, Stephen James (2002). The Caldwell objects. Cambridge, USA: Sky Publishing Corporation. p. 378. ISBN 0-933346-97-2. 
  5. ^ Thackeray, A. D. (1949). "The Kappa Crucis Cluster". Monthly Notes of the Astronomical Society of South Africa 8: 30. Bibcode:1949MNSSA...8...30T. 
  6. ^ Judge, Harry George; Toyne, Anthony (1993). Oxford Illustrated Encyclopedia, Volume 8. p. 76. 
  7. ^ Feast, M. W. (1963). "The galactic cluster NGC 4755 (κ Crucis)". Monthly Notices of the Royal Astronomical Society 126: 11. Bibcode:1963MNRAS.126...11F. 
  8. ^ Burnham, Robert (1978). Burnham's Celestial Handbook: An Observer's Guide to the Universe Beyond the Solar System. New York: Dover Publications. p. 730. ISBN 978-0-486-23568-4. 
  9. ^ a b Consolmagno, Guy; Davis, Dan (2005). Turn left at Orion: a hundred night sky objects to see in a small telescope. Cambridge, United Kingdom: University of Cambridge. p. 189. ISBN 0-521-78190-6. 
  10. ^ Kaler, James B. (1989). Stars and their spectra: an introduction to the spectral sequence. University of Cambridge. p. 13. ISBN 0 521 30494 Check |isbn= value (help). 
  11. ^ a b c Inglis, Mike (2004). Astronomy of the Milky Way: The observer's guide to the southern Milky Way. Springer. pp. 78–79. ISBN 1-85233-709-5. 
  12. ^ Ridpath, Ian; Tirion, Wil (2007). Stars and Planets. p. 134. ISBN 978-0-691-13556-4. 
  13. ^ Mobberley, Martin (2009). The Caldwell Objects. Springer. p. 196. doi:10.1007/978-1-4419-0326-6. ISBN 978-1-4419-0325-9. 

External links [edit]

Coordinates: Sky map 12h 53m 42s, −60° 22′ 00″
List
See also
Retrieved from "http://en.wikipedia.org/w/index.php?title=Jewel_Box_(star_cluster)&oldid=543421515"