Jewel Box (star cluster)

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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] (1.968 kpc[3])
Physical characteristics
Mass - M☉
Radius -
Estimated age 16Myr[3]
Notable features -
Other designations NGC 4755,[1] Herschel's Jewel Box,[1]
Kappa Crucis Cluster,[1] Caldwell 94[4]
See also: Open cluster, List of open clusters

The Jewel Box, Kappa Crucis Cluster, NGC 4755, is an open cluster in the constellation Crux, originally discovered by Nicolas Louis de Lacaille during 1751–1752. This famous cluster was later named the Jewel Box by Sir John Herschel when he described its telescopic appearance as "...a superb piece of fancy jewellery" It is easily visible to the naked eye as a hazy star some 1.0° southeast of the first-magnitude star Beta Crucis. This hazy star was given the Bayer star designation Kappa Crucis, from which the cluster takes one of its common names. The modern designation Kappa Crucis has been assigned to one of the stars in the base of the A-shaped asterism of the cluster, the third brightest cluster star (HD 111973, HIP 62931, HR 4890), located at the base of the right leg of the A. This is a blue supergiant of spectral type B3Iae, shining at the apparent photometric visual magnitude of 5.94V. Two other cluster stars are brighter than κ Cru, namely, 5.77 magnitude star HD 111904 (HIP 62894), at the tip of the A, and HD 111613 (HIP 62732) at 5.75, which is 15 arc minutes beyond the asterism toward Beta Crucis.[5]

This cluster is one of the youngest known, with an estimated age of 14 million years. It has a total integrated magnitude of 4.2, is located 6,440 light years from Earth, and contains around 100 stars.

Discovery and observation

The Jewel Box as a star cluster was first determined by Nicolas Louis de Lacaille while he was doing his South African astrometric observations for his star catalogue. 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 many stars.[6][7] The name "Jewel Box" comes from John Herschel's description of it: "...this cluster, though neither a large nor a rich one, is yet an 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"[6]

Herschel recorded the positions of 100 members of the cluster in 1834–1838.[8]

Physical characteristics

The Jewel Box cluster is one of the youngest known open clusters. The mean radial velocity of the Jewel Box cluster is −21 kilometres per second (−13 mi/s).[3] The brightest stars in the Jewel Box cluster are supergiants, and include some of the brightest stars in the Milky Way galaxy.[9]

Calculating its distance is difficult due to the proximity of the Coalsack Nebula, which obscures some of its light.[10]

Observation

The Jewel Box cluster is regarded as one of the finest objects in the southern sky.[11] It is visible to the naked eye as a hazy object of the fourth magnitude.[12] It can be easily located using the star Beta Crucis as a guide, and appears as a fourth magnitude object.[13] It is impressive when viewed with binoculars or a small or large telescopes. The three brightest members of the cluster lie in a straight line known as the 'traffic lights' due to their varying colours.[14]

Gallery

  • 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

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Lua error in package.lua at line 80: module 'strict' not found.
  2. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  3. ↑ 3.0 3.1 3.2 Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ http://www.southastrodel.com/Page002.htm, NGC 4755 : The Jewel Box "The Jewel of the South" : Introduction
  6. ↑ 6.0 6.1 http://www.docdb.net/show_object.php?id=ngc_4755, DOCdb : Jewel Box
  7. ↑ http://www.southastrodel.com/Page004.htm, History of the Jewel Box Part One : 1752-1834
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  12. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  13. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  14. ↑ Lua error in package.lua at line 80: module 'strict' not found.

External links

Coordinates: Sky map 12h 53m 42s, −60° 22′ 00″

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