Jewel Box (star cluster)
NGC 4755 taken by the VLT
|Observation data (J2000 epoch)|
|Right ascension||12h 53m 42s|
|Distance||6.4 kly (1.98 kpc)|
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.
Discovery and observation 
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. 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"
Herschel recorded the positions of 100 members of the cluster in 1834–1838.
Physical characteristics 
The Jewel Box cluster is regarded as one of the finest objects in the southern sky. It is visible to the naked eye as a hazy object of the fourth magnitude. The Jewel Box cluster can be easily located using the star Beta Crucis as a guide, and appears as a fourth magnitude object. The three brightest members of the cluster lie in a straight line known as the 'traffic lights' due to their varying colours.
Hubble image of the Jewel Box.
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- A Copyright Anglo-Australian Observatory Image of NGC 4755
- The Jewel Box on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images
- A Copyright T. Warner Amateur Image of NGC4755