Jewel Box
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This article is about the star cluster. For other meanings see Jewel box.
| Observation data: J2000 epoch | |
|---|---|
| Class: | |
| Constellation: | Crux |
| Right ascension: | 12h 53m 42s[1] |
| Declination: | -60° 22.0′[1] |
| Distance: | 6.4 kly[2] (1.98 kpc) |
| Apparent magnitude (V): | |
| Apparent dimensions (V): | |
| Physical characteristics | |
| Mass: | (- M☉) |
| Radius: | - |
| VHB: | - |
| Estimated age: | - |
| 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 or Kappa Crucis Cluster) is an open cluster in the Crux constellation. As Kappa Crucis, it has a Bayer designation despite the fact that it is a cluster rather than an individual star.
It was 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 7.1 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 bright orange star is kappa Crucis, and it contrasts strongly against its predominantly blue, hot companions. Kappa Cru is a very large, (hence very luminous) quite young star in its red supergiant stage, which paradoxically indicates that its life is drawing to a close. The cluster looks like a star to the unaided eye and appears close to the eastern-most star of the Southern Cross (Beta Crucis), so is only visible from southern latitudes.
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