A Casket of Precious Stones

NGC 4755 – Jewel Box Cluster (Re-Imaged)


NGC 4755 is one of the finest objects in the Southern Sky. An open cluster in the constellation Crux, the Southern Cross and known as both the Jewel Box and the Kappa Crucis cluster.
Discovered by Nicolas Louis de Lacaille during his 1751-1752 visit to South Africa. John Herschel described this famous group of bright young stars as “a casket of variously coloured precious stones” in his telescope; the name “Jewel Box” derives from this description.

Only visible from southern latitudes, and appears close to Beta Crucis, the easternmost star of the Southern Cross. It has an apparent magnitude of 4.2, and looks like a single star to the unaided eye. The cluster contains around 100 stars within a 10' diameter area. Most are blue giants; the brightest is κ Cru, a blue supergiant of visual magnitude 5.9 and spectral type B5 Ia. The fourth-brightest is a magnitude 7.6 red supergiant of class M2 Iab that contrasts strongly against its hot, blue companions.

A very young cluster, with an estimated age of only 7.1 million years. Distance estimates for the Jewel Box range from 6,400 to 8,150 light years.

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Imaged 20 February 2013 @ 2100
Canon 7D Prime Focussed in Celestron CPC 925
ISO 800
Exposure 15 sec

 


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