Jewel Box (star cluster)
| Jewel Box | |
|---|---|
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| Observation data (J2000 epoch) | |
| Constellation | Crux |
| Right ascension | 12h 53m 42s |
| Declination | −60° 22.0′ |
| Distance | 6.4 kly (1.968 kpc) |
| Physical characteristics | |
| Mass | - M☉ |
| Radius | - |
| Estimated age | 16Myr |
| Notable features | - |
| Other designations |
NGC 4755, Herschel's Jewel Box, |
NGC 4755, Herschel's Jewel Box,
The Jewel Box (also known as Kappa Crucis Cluster or NGC 4755) is an open cluster in the constellation Crux, originally discovered by Nicolas Louis de Lacaille in 1751–1752. This cluster was later named the Jewel Box by 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
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 1.95 kpc. or 6,440 light years from Earth, and contains just over 100 stars.
The Jewel Box as a star cluster was first found by Nicolas Louis de Lacaille while doing astrometric observations for his 1751-1752 southern star catalogue Cœlum Australe Stelliferum at the Cape of Good Hope in South Africa. He saw this as a nebulous cluster in his small 12mm. (½-inch) telescope, but was first to recognise it as a group of many stars. The name "Jewel Box" comes from John Herschel's own description 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"
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