The Southern Cross, or Crux, is a constellation visible throughout the southern hemisphere and the equatorial regions, which can be found between the neighbouring constellations of Centaurus and Musca. Stargazers should be careful not to confuse the Southern Cross with another similar constellation, the False Cross.
– Finding the Southern Cross –
The Crux or Cross is shaped like a kite, and made up of five stars. (The nearby and similar False Cross constellation contains only four.) Because there is no southern star equivalent to the North Star, Polaris, the Southern Cross, because of its fairly uniform southern location, was once the major reference point for star navigation in the southern hemisphere.
– Composition –
Like all constellations, the Southern Cross is made up of stars which do not necessarily have anything in common with each other except for the pattern they form when viewed from Earth. In the case of the Southern Cross, Acrux (the brightest star in the constellation), Delcrux, and Mimosa are part of what is called a stellar association, or former open star cluster, roughly between 300 and 400 light-years from the solar system. Acrux itself is actually a binary system consisting of two very hot blue stars, each much brighter than our own Sun; from this distance, they appear to be a single star to the naked eye.
The other two member stars of the constellation are unrelated to these three or to their broader group. Gacrux, a dying red giant star, is located just 90 light-years away from us. The last of the member stars, Eta Crucis, is smaller still, a yellow giant star somewhat larger than our own Sun which is located just 60 light-years away. In comparison, our closest neighbours, in the Centauri trinary system, are located 4 light-years away from us.
– History and Culture –
Its usefulness meant it was recognized by quite a variety of ancient and indigenous cultures. Several thousand years ago, the Southern Cross could still be viewed from the northern hemisphere, and was therefore identified by the Ancient Greeks; however, Europe’s Mediterranean cultures lost sight of the Crux for the last time during the collapse of the Roman empire, as it migrated south of the equator relative to stargazers on the Earth.
Other cultures in the south have known the Southern Cross by different names. For example, Australian aborigines called the cross the Emu or the god Mirrabooka, while the Incans in South America knew it as the Stairs, the New Zealand Maori called it the Anchor, and the African Tuaregs know it as the Four Trees. Today, the cross can be found on the national flags of both Australia and New Zealand.
