Saturday, 13 June 2009

Southern Cross

The Southern Cross can always be seen from New Zealand and is the most recognised constellation in the Southern Hemisphere.
Southern Cross
is the English name of Crux Australis, a constellation visible in the Southern Hemisphere.

Crux (pronounced /ˈkrʌks/, genitive Crucis /ˈkruːsɨs/) is the smallest of the 88 modern constellations, but is one of the most distinctive. Its name is Latin for cross, and it is dominated by a cross-shaped asterism that is commonly known as the Southern Cross because throughout this Common Era it has been easily visible from the southern hemisphere, at practically any time of year, although it is also visible near the horizon from tropical latitudes of the northern hemisphere, for a few hours every night, during the spring months; for instance, from Cancun -- or any other place al latitude 25º N or less, with unobstructed view to the South—at around 10 pm, at the end of April.

Crux is bordered by the constellations Centaurus, which surrounds it on three sides, and Musca.

Crux was visible to the Ancient Greeks, who regarded it as part of the constellation Centaurus. At the latitude of Athens in 1000 BC, Crux was clearly visible, though low in the sky. However, the precession of the equinoxes gradually lowered its stars below the European horizon, and they were eventually forgotten by the inhabitants of northern latitudes. By AD 400, most of the constellation never rose above the horizon for Athenians.

Crux was rediscovered by Europeans during the Age of Discovery. Amerigo Vespucci mapped Alpha Centauri and Beta Centauri as well as the stars of modern Crux on his expedition to South America in 1501.

The separation of Crux from Centaurus is generally attributed to the French astronomer Augustin Royer in 1679. Other historians attribute the invention of Crux to Petrus Plancius in 1613, noting that the constellation was later published by Jakob Bartsch in 1624.

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