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Crux

Crux Australis, The Cross, The Southern Cross

Constellation of the southern sky

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GenitiveCrucis
AbbreviationCru
Right Ascension11h53 to 12h55
Declination-55.5° to -64.5°
Area (sq deg)68
Brightest StarAcrux
Optimum VisibilityApril
Map of Crux
Relative Galactic Position of Crux

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

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.

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; perhaps 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 naked eye.

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