Britain could once see the Southern Cross, until Earth's wobble hid it
Around the fourth millennium BC, people as far north as Britain could watch the whole Southern Cross rise. The slow wobble of Earth's axis then dragged it below European horizons, and by 400 AD most of the continent had lost sight of it. Europeans only rediscovered the little cross when their ships pushed south.
Crux is the smallest of the 88 official constellations, yet one of the easiest to pick out, because all four stars of its cross shine brighter than magnitude 2.8. The brightest, blue-white Acrux at magnitude 0.8, marks the southern tip; Mimosa and Gacrux are among the others. Several belong to a loose family of hot blue-white stars, the Scorpius-Centaurus association, that seem to share a birthplace. Nearby sparkle the Jewel Box cluster and, just southeast, the Coalsack, a dark cloud about 7 by 5 degrees across.
Ptolemy knew these stars but folded them into Centaurus. Dante's Divine Comedy describes four bright southern stars, though that may be allegory rather than astronomy. The Venetian Alvise Cadamosto probably glimpsed the cross when leaving the Gambia River in 1455 and called it the southern chariot, but his sketch was wrong. João Faras gets credit for the first accurate European drawing, in a letter to the Portuguese king written on a Brazilian beach on 1 May 1500.
Mapmakers took longer. Emery Molyneux and Petrus Plancius both showed it as its own constellation in 1592, though in the wrong place. Globes by Plancius and Jodocus Hondius finally positioned it correctly around 1598 and 1600, and Frederick de Houtman catalogued its stars separately from Centaurus in 1603.
Southern peoples had long read their own stories into it. In several Aboriginal Australian traditions, Crux and the Coalsack form the head of the Emu in the Sky, a figure traced in dark gaps between stars; the Yolngu of Arnhem Land see a stingray. Māori call it Māhutonga, the anchor of a great canoe formed by the Milky Way. In Indonesia and Malaysia it is the ray star, and in Tonga a duck flying south with an injured wing. Today it features in the cultural identity of many Southern Hemisphere nations.
Source: Crux
