Crux, or the Southern Cross, is a prominent constellation in the southern sky. It is the smallest of all 88 constellations.
In spite of its size, Crux is one of the best known constellations in the southern hemisphere. It is easily recognizable for the cross-shaped asterism, the Southern Cross, formed by its five brightest stars. The constellation is associated with a number of stories and it figures prominently in different mythologies in the southern hemisphere. It holds special importance in Australia and New Zealand, where it is circumpolar and can be seen throughout the year.
Crux is not visible north of +20° in the northern hemisphere, and it is circumpolar south of 34°S, which means that it never sets below the horizon. On the celestial sphere, Crux is exactly opposite the constellation Cassiopeia.
Crux means “the cross” in Latin. Ancient Greeks considered Crux to be a part of the constellation Centaurus. Even though its stars were charted on most celestial globes, it was not until 1679 that it became a constellation in its own right. It was the French astronomer Augustin Royer who formally separated Crux from Centaurus. Some historians credit the Dutch astronomer Petrus Plancius for creating the constellation in 1613, as it was published by Jakob Bartsch in 1624.
FACTS, LOCATION & MAP
Crux is the smallest of the 88 constellations, occupying an area of only 68 square degrees. It is located in the third quadrant of the southern hemisphere (SQ3) and can be seen at latitudes between +20° and -90°. The neighboring constellations are Centaurus and Musca.
Crux belongs to the Hercules family of constellations, along with Aquila, Ara, Centaurus, Corona Australis, Corvus, Crater, Cygnus, Hercules, Hydra, Lupus, Lyra, Ophiuchus, Sagitta, Scutum, Sextans, Serpens, Triangulum Australe, and Vulpecula.
Crux has one star with known planets and contains no Messier objects. The brightest star in the constellation is Acrux, Alpha Crucis, with an apparent magnitude of 0.77. Acrux is also the 12th brightest star in the sky. There is one meteor shower associated with the constellation; the Crucids.
MYTHOLOGY
Crux is a famous constellation in many cultures. Ancient Greeks considered it to be part of the Centaurus constellation. Greeks were able to see Crux before its stars dropped below the horizon for Europe and most of the northern hemisphere. Some saw significance in this, linking the disappearance of the celestial cross from the sky to the crucifixion of Christ. The 2nd century Greek astronomer Ptolemy listed the stars of Crux as part of the constellation Centaurus in his Almagest. By the year 400 AD, the constellation was not visible from most of Europe anymore, and Europeans did not rediscover Crux until the great naval expeditions of the late 15th and early 16th century.
The Southern Cross carries cultural significance in many countries in the southern hemisphere.
A stone image of Crux constellation has been found in Machu Picchu in Peru. The Inca knew the constellation as Chakana, which means “the stair.” The Maori called it Te Punga, or “the anchor.”
In Australian Aboriginal astronomy, the cross asterism and the Coalsack Nebula represent the head of the Emu in the Sky. The Southern Cross is represented on the Australian flag. Its stars are also featured on the flag of Brazil, where the asterism is known as Cruzeiro, or Cruzeiro do Sul. The Southern Cross is also mentioned in the Brazilian national anthem and used to be the name of the currency between 1942 and 1986 and again between 1990 and 1994.
Amerigo Vespucci charted the stars in 1501, but a more accurate depiction appeared in 1515, made by another Italian explorer, Andrea Corsali. Crux appeared on celestial globes by Petrus Plancius (1598) and Jodocus Hondius (1600). Plancius, a Dutch cartographer, depicted the constellation based on observations by Pieter Dirkszoon, a Dutch explorer.
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