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The Jewel Box Cluster
By Jeff Kanipe
posted: 30 June 2005
08:12 am
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Friday, June 15Lying just south of the bright star Mimosa in Crux the Southern Cross is a coarse aggregate of 50 blue and red stars that on the whole resemble a flashy necklace of rubies and sapphires. | Ask the Astronomer | | Have a question for columnist Jeff Kanipe? Now you can Ask the Astronomer. | This bespangled object is the Jewel Box Cluster or, as it is cataloged, NGC 4755. Like the Double Cluster, it too is fairly young in age, about 10 million years, but lies at a greater distance, about 8,800 light-years. The Jewel Box is one of the loveliest open clusters in the southern sky. Its brightest members, including 6th-magnitude Kappa Crucis, form a wedge-shaped pattern, confined to an area of sky smaller than the apparent diameter of the full Moon. At the center of the cluster a brilliant 7th-magnitude red supergiant provides a startling color contrast to the surrounding blue and white stars. The bulk of the fainter members lie south and southeast of the clusters center. The Jewel Box can be seen with the unaided eye in a dark sky but is best observed using binoculars or a low-power telescope. Too much magnification will uncluster the cluster. The region surrounding the Jewel Box is equally remarkable. Just south lies the starless void of the Coal Sack, a cloud of dense interstellar dust and one of the nearest of the dark nebulae. This also is apparent to the naked eye. Binoculars also reveal many dark lanes and dust filaments in and around the Jewel Box, the raw material of stars yet to be. Jewel Box Stats: - Magnitude: 4.2
- Apparent size: 10 arcminutes
- True size: 25 light-years in diameter
- Distance: 8,800 light-years
- Interesting fact: contains a blue supergiant 80,000 times more luminous than the Sun
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