The Jewel Box (NGC 4755)

NGC 4755 is an open cluster in the constellation Crux, the Southern Cross. It is known as both the Jewel Box and the Kappa Crucis cluster.

This cluster is one of the finest objects 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 colored precious stones” in his telescope; the name “Jewel Box” derives from this description.

This cluster has an apparent magnitude of 4.2, and looks like a single star to the naked 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. The fourth brightest is a magnitude 7.6 red supergiant of class M2 that contrasts strongly against its hot, blue companions. This cluster is one of the youngest known, 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.

RA 12h 53m 38.7s
DEC -60° 20’ 56 ».6
ORIENTATION Up is 359 degrees E of N
CONSTELLATION Crux
DISTANCE 6,400 ly

Captured September 2021
Fiel Of view: 25.8 x 25.8 arcmin
Total integration time of 10.8 hours