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CRUX
The Southern Cross
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The Southern Cross is the most well known and easily recognized constellation in the southern sky. You have to be south of 25 degrees north latitude to see it, but if you are far enough south, you can't miss the four bright stars that make up the shape of a cross. A common misconception is that the Southern Cross contains the southern sky equivalent of the North Star, Polaris. The truth is there are no stars close enough to the south celestial pole to be called the "South Star", and the Southern Cross is not even close. It does point the way, however. If you follow an imaginary line along the vertical axis of the cross four and a half lengths to the south, you will be very close to the south celestial pole.
The southern Cross basically sits right in the middle of the Milky Way, and is surrounded by rich star fields and dark nebulae. Just below the cross is a large dark nebula known as the Coal Sack. It is an area of thick interstellar dust 600 light years away that measures a vast 35 light years across, and blocks all the light from the stars behind it. It is so large and prominent, it is visible with the naked eye. The Coal sack is very evident in the photo below, as is the brilliant Alpha Centauri, in the constellation Centaurus, at the far lower left of the photo.
The Southern Cross also contains one of the most spectacular star clusters in the sky, NGC 4755, also known as the Jewel Box. It is a grouping of over 100 stars, 6,500 light years away. Most of the stars are very young, and sparkle with varying shades of blue. One notable exception is the prominent, bright orange supergiant Kappa Crucis. This star is so distinctive, the entire group is sometimes called the Kappa Crucis Cluster.
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