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jewelbox.jpgJewelbox.2224 viewsThe 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 7.1 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 bright orange star Kappa Crucis contrasts strongly against its predominantly blue, hot companions. Kappa Crucis is a very large (hence very luminous) young star in its red supergiant stage, which paradoxically indicates that its life is drawing to a close. 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.Martin

testing.jpgtestimage1047 views2X30Seconds at ISO1600Martin

CentAfinal2G.jpgCentaurus A1156 views10 X 5 Min RGB and 15 X 10 Min Luminance.
Martin

IMG_0507.jpg298 viewsLooking down at Italians flat 2Martin

etaha-2.jpgEta Carinae in HA.659 viewsThis stellar system is currently one of the most massive that can be studied in great detail. Until recently, Eta Carinae was thought to be the most massive single star, but it was recently demoted to a binary system.[7] The most massive star in the Eta Carinae multiple star system has more than 100 times the mass of the Sun. Other known massive stars are more luminous and more massive.

Stars in the mass class of Eta Carinae, with more than 100 times the mass of the Sun, produce more than a million times as much light as the Sun. They are quite rare — only a few dozen in a galaxy as big as the Milky Way. They are assumed to approach (or potentially exceed) the Eddington limit, i.e., the outward pressure of their radiation is almost strong enough to counteract gravity. Stars that are more than 120 solar masses exceed the theoretical Eddington limit, and their gravity is barely strong enough to hold in their radiation and gas.

Eta Carinae's chief significance for astrophysics is based on its giant eruption or supernova impostor event, which was observed around 1843. In a few years, Eta Carinae produced almost as much visible light as a supernova explosion, but it survived. Other supernova impostors have been seen in other galaxies, for example the false supernovae SN 1961v in NGC 1058[8] and SN 2006jc in UGC 4904,[9] which produced a false supernova, noted in October 2004. Significantly, SN 2006jc was destroyed in a supernova explosion two years later, observed on October 9, 2006.[10] The supernova impostor phenomenon may represent a surface instability[11] or a failed supernova. Eta Carinae's giant eruption was the prototype for this phenomenon, and after nearly 170 years the star's internal structure has not fully recovered.Martin