Crux

Crux is a constellation in the southern sky, built around four bright stars that form a cross-shaped pattern widely called the Southern Cross. It sits at the southern edge of the Milky Way’s visible band. Although it is the smallest of the 88 modern constellations, Crux is one of the easiest to recognize because all four of its main stars shine brighter than magnitude +2.8. The constellation carries deep cultural importance across many Southern Hemisphere countries and communities.

The brightest star in Crux is blue-white α Crucis, also known as Acrux, with a magnitude of 0.8; it is also the southernmost of the four. Moving clockwise, the other three main stars are β Crucis (Mimosa), γ Crucis (Gacrux), and δ Crucis (Imai), each slightly dimmer than the last. A fifth star, ε Crucis (Ginan), also lies within the cross asterism. Many of these brighter stars belong to the Scorpius–Centaurus association, a large, loose group of hot, blue-white stars that likely share a common origin and motion across the southern Milky Way.

Crux contains four Cepheid variable stars, all visible to the naked eye under good conditions. On its eastern border lies the Jewel Box (NGC 4755), a bright and colorful open cluster. To the southeast stretches the Coalsack Nebula, a large dark nebula spanning 7° by 5°, with parts extending into the neighboring constellations Centaurus and Musca.

The bright stars of Crux were known to the Ancient Greeks, who included them in the constellation Centaurus. In the fourth millennium BC, they were fully visible as far north as Britain. Over time, precession of the equinoxes lowered these stars below the European horizon, and they were eventually forgotten by northern observers. By 400 AD, they never rose above the horizon in most of Europe. In the 14th century, Dante may have referenced them in his *Divine Comedy*, describing four bright stars in the southern sky, though this could be allegorical or coincidental.

In 1455, Venetian navigator Alvise Cadamosto noted what was probably the Southern Cross while leaving the Gambia River, calling it the *carro dell'ostro* ("southern chariot"), but his diagram was inaccurate. Historians generally credit João Faras as the first European to correctly depict it; he sketched and described the constellation (calling it "las guardas") in a letter written from Brazil on 1 May 1500 to the Portuguese king. Explorer Amerigo Vespucci likely observed both the Southern Cross and the Coalsack Nebula on his second voyage in 1501–1502. Italian navigator Andrea Corsali, sailing to China and the East Indies between 1515 and 1517, wrote a letter in 1516 to King Manuel I that included a crude map of southern stars, showing the Southern Cross and the two Magellanic Clouds as seen from outside a globe.

Emery Molyneux and Petrus Plancius are sometimes cited as the first uranographers to treat Crux as a separate constellation, with representations from 1592—Molyneux on a celestial globe and Plancius on a wall map. However, both relied on unreliable sources and placed Crux incorrectly. The constellation first appeared in its correct position on celestial globes by Petrus Plancius and Jodocus Hondius in 1598 and 1600. Frederick de Houtman separately catalogued its stars from Centaurus in 1603. The constellation was later adopted by Jakob Bartsch in 1624 and Augustin Royer in 1679, though Royer is sometimes wrongly credited as the first to distinguish it.

In Indian tradition, a story tells of the creation of Trishanku Swarga, meaning Cross (Crux), by the sage Vishwamitra. In Chinese astronomy, the asterism 十字架 (Shí Zì Jià), meaning Cross, consists of γ Crucis, α Crucis, β Crucis, and δ Crucis. In Australian Aboriginal astronomy, Crux and the Coalsack mark the head of the Emu in the Sky (seen in dark spaces rather than star patterns) in several cultures. Crux itself is described as a possum in a tree (Boorong people of northwestern Victoria), the sky deity Mirrabooka (Quandamooka people of Stradbroke Island), a stingray (Yolngu people of Arnhem Land), or an eagle (Kaurna people of the Adelaide Plains). Two Pacific constellations also included Gamma Centauri. Torres Strait Islanders saw Gamma Centauri as the handle and the four cross stars as the left hand of Tagai, with the stars of Musca as the trident of his fishing spear. In Aranda traditions of central Australia, the four cross stars are the talon of an eagle, and Gamma Centauri is its leg.

Various peoples in the East Indies and Brazil viewed the four main stars as the body of a ray. In Indonesia and Malaysia, it is known as Bintang Pari and Buruj Pari, respectively ("ray stars"). This aquatic theme also appears in an archaic Vietnamese name, *sao Cá Liệt* (the ponyfish star). Among Filipino people, the Southern Cross has names related to tops, including *kasing* (Visayan), *paglong* (Bikol), and *pasil* (Tagalog), and is also called *butiti* (puffer fish) in Waray. The Javanese people of Indonesia called this constellation *Gubug pèncèng* ("raking hut") or *lumbung* ("the granary").