Constellation Chart

Crux Australis, The Cross, The Southern Cross

Stars:

Crux lies within a densely populated area of the Milky Way, and so in a densely starred region. As one might imagine from its name, the body of the Cross is made up of four bright stars, Alpha, Beta, Gamma and Delta Crucis. Though Delta Crucis does not appear to have a proper name, its three brighter companions do: they are known as Acrux, Becrux and Gacrux, respectively. These are, without doubt, the three least inspired star names in the entire sky. These four main stars lie between 200 and 600 light years (about 60 and 180 parsecs) from Earth. Much further away, at around 7,600 light years (2,300 parsecs) lies an open cluster known as the Jewel Box that is just visible to the with the eye.

Derivation:

All constellations are in some sense artificial, but while many, especially in the northern sky, date back thousands of years and have rich histories, the elegant Southern Cross has a disappointingly prosaic derivation. In the late seventeenth century, Royer (or, according to some sources, Abbé de la Caille) simply carved a rectangular region of sky out of Centaurus and renamed it Crux (Latin for 'Cross').

Crux is often called the Southern Cross (Crux Australis) to distinguish it from the 'Northern Cross', a traditional, but entirely unofficial, name for the bright stars that make up Cygnus in the northern sky.

With an area of less than seventy square degrees, Crux has the distinction of being the smallest constellation in the sky. It occupies only about one twentieth of the area of Hydra, the largest of the constellations.

Tiny Crux carves out a thin sliver of space within the plane of the Milky Way.

Galaxies In Crux

NGC4755

This cluster was one of the finest open clusters discovered by Abbe 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 (Sky Catalog 2000). Its hottest star is of spectral type B0. According to Burnham, the 3 brightest stars are blue giants of mag 5.75 and spectral type B9, mag 5.94 and type B3, and mag 6.80/B2, while the fourth brightest star is a mag 7.58 M2 red supergiant. Another mag 5.7/spectral type A1 star is probably also a member, another white supergiant: This star would be the brioghtest of the cluster at about absolute magnitude -7.7 (83,000 solar luminosities).

Situated close to the cluster is a huge dark area of the sky, right within the band of the Milky Way: the Coal Sack. This is a huge dark nebula, probably the nearest at 500 to 600 light years distance, and 60 to 70 light years diameter.

The Coal Sack

The Coal Sack is a large dark nebula only 550 light years away, just to the south of the Jewel Box, visible to the normal vision.

Dark nebulae are massive clouds of interstellar gases and dust, dense enough to block out most of the light from stars behind it. The Coal Sack and Horsehead Nebulae (in Orion) are the two best known dark nebulae; of all dark nebulae, the Coal Sack is the largest one visible to the unaided eye.

Deep Sky Objects in Crux:

"Brilliant" is the word usually used to describe The Jewel Box (NGC 4755). Also called the Kappa Crucis star cluster, this open cluster is composed of over a hundred stars, about fifty of which are a mixture of colourful supergiants: reds and blues intermingled with yellows and whites in a profusion of sparkling light.

The cluster is just a baby, perhaps no older than ten million years. Many of the stars have very high luminosities, approaching 100,000 Suns. The central star is kappa Crucis, a blue sixth-magnitude supergiant. The cluster is considered to be from 6800 to 7800 light years away. To locate The Jewel Box, find beta Crucis and drop down to the southeast one and a half degrees.

Planetary Destinations In Crux

HD 108147

Parent Star: HD 108147 (F8/G0 V) in the constellation of Crux is located at a distance of 125.8 Light Years from our Solar system Co-ordinates are Right Ascension: 12 25 46.2686 & Declination: -64 01 19.516. The apparent Magnitude of the star is 6.99. The Inner Edge of Habitability Zone is 0.7 AU & the Outer Edge of Habitability Zone: 2.19 AU. Orbiting around HD 108147 is planet HD 108147 b is believed to be a Dark Hot Jupiter, Eccentric and its exitence has been confirmed. The Planets Appearance is Dark sodium haze. The planet is positioned out side of Habitability Zone at Mean Orbital Distance of 0.104 AU. The planet Orbits around the star every 10.901 ± 0.001 Days and was discovered by Michel Mayor, Dominique Naef, Francesco Pepe, Didier Queloz, Nuno Santos, Stephane Udry and Michel Burnet in 2000.