Canopus is the brightest star in the southern constellation of Carina and is located near the western edge of the constellation around 310 light-years from the Sun.
Its proper name is generally considered to originate from the mythological Canopus, who was a navigator for Menelaus, king of Sparta. Canopus has the Bayer designation α Carinae, which is Latinised to Alpha Carinae and abbreviated Alpha Car or α Car.
It is the second-brightest star in the night sky, after Sirius. Canopus’ visual apparent magnitude is −0.74, and it has an absolute magnitude of −5.71.
Canopus is an aging bright giant of spectral type A9 or F0, so it is essentially white when seen with the naked eye. Canopus is undergoing core helium burning and is currently in the so-called blue loop phase of its evolution, having already passed through the red-giant branch after exhausting the hydrogen in its core.
Canopus has eight times the mass of the Sun and has expanded to 71 times the Sun’s radius. It is radiating over 10,000 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of around 7,000 K. Canopus is an X-ray source, which is likely being emitted from its corona.
The prominent appearance of Canopus means it has been the subject of mythological lore among many ancient peoples. The acronychal rising marked the date of the Ptolemaia festival in Egypt.
In Hinduism, it was named Agastya after the revered Vedic sage. For Chinese astronomers, it was known as the Old Man of the South Pole.
In Indian Vedic literature, Canopus is associated with the sage Agastya, one of the ancient siddhars and rishis (the others are associated with the stars of the Big Dipper). To Agastya, the star is said to be the ‘cleanser of waters‘, and its rising coincides with the calming of the waters of the Indian Ocean.
It is thus considered the son of Pulastya, son of Brahma. Canopus is described by Pliny the Elder and Gaius Julius Solinus as the largest, brightest and only source of starlight for navigators near Tamraparni island (ancient Sri Lanka) during many nights.
Canopus was not visible to the mainland ancient Greeks and Romans; it was, however, visible to the ancient Egyptians. Hence Aratus did not write of the star as it remained below the horizon, while Eratosthenes and Ptolemy—observing from Alexandria—did, calling it Kanōbos.
The Navajo named it Ma’ii Bizò‘. In the Guanche mythology of the island of Tenerife (Spain), the star Canopus was linked with the goddess Chaxiraxi.
The Bedouin people of the Negev and Sinai also knew Canopus as Suhayl and used it and Polaris as the two principal stars for navigation at night. Because it disappears below the horizon in those regions, it became associated with a changeable nature, as opposed to always-visible Polaris, which was circumpolar and hence ‘steadfast’.
The Spanish Muslim astronomer Ibn Rushd went to Marrakesh (in Morocco) to observe the star in 1153, which is invisible in his native Córdoba, Al-Andalus. He used the different visibility in different latitudes to argue that the earth is round, following Aristotle‘s argument which held that such an observation was only possible if the earth was a relatively small sphere.
Called the Old Man of the South Pole in Chinese, Canopus appears (albeit misplaced northwards) on the medieval Chinese manuscript the Dunhuang Star Chart, although it cannot be seen from the Chinese capital of Chang’an.
The Chinese astronomer Yi Xing had journeyed south to chart Canopus and other far southern stars in 724 AD. However, it was already mentioned by Sima Qian in the second century BC, drawing on sources from the Warring States period, as the southern counterpart of Sirius.
Bright stars were important to the ancient Polynesians for navigation between the many islands and atolls of the Pacific Ocean. Low on the horizon, they acted as stellar compasses to assist mariners in charting courses to particular destinations.
Canopus served as the southern wingtip of a “Great Bird” constellation called Manu, with Sirius as the body and Procyon the northern wingtip, which divided the Polynesian night sky into two hemispheres.
The Hawaiian people called Canopus Ke Alii-o-kona-i-ka-lewa, “The chief of the southern expanse”; it was one of the stars used by Hawaiʻiloa and Ki when they traveled to the Southern Ocean.
The Māori people of New Zealand/Aotearoa had several names for Canopus. Ariki (“High-born”), was known as a solitary star that appeared in the east, prompting people to weep and chant. They also named it Atutahi, Aotahi or Atuatahi, “Stand Alone”. Its solitary nature indicates it is a tapu star, as tapu people are often solitary.
Its appearance at the beginning of the Maruaroa season foretells the coming winter; light rays to the south indicate a cold wet winter, and to the north foretell a mild winter. Food was offered to the star on its appearance. This name has several mythologies attached to it. One story tells of how Atutahi was left outside the basket representing the Milky Way when Tāne wove it.
Another related myth about the star says that Atutahi was the first-born child of Rangi, who refused to enter the Milky Way and so turned it sideways and rose before it. The same name is used for other stars and constellations throughout Polynesia.
The Tswana people of Botswana knew Canopus as Naka. Appearing late in winter skies, it heralded increasing winds and a time when trees lose their leaves. Stock owners knew it was time to put their sheep with rams. In southern Africa, the Sotho, Tswana and Venda people called Canopus Naka or Nanga, “the Horn Star”, while the Zulu and Swazi called it inKhwenkwezi “Brilliant star“.
It appears in the predawn sky in the third week of May. According to the Venda, the first person to see Canopus would blow a phalaphala horn from the top of a hill, getting a cow for a reward. The Sotho chiefs also awarded a cow and ordered their medicine men to roll bone dice and read the fortune for the coming year.
The Kalapalo people of Mato Grosso state in Brazil saw Canopus and Procyon as Kofongo “Duck“, with Castor and Pollux representing his hands. The asterism’s appearance signified the coming of the rainy season and increase in manioc, a food staple fed to guests at feasts.
Canopus traditionally marked the rudder of the ship Argo Navis. English explorer Robert Hues brought it to the attention of European observers in his 1592 work Tractatus de Globis, along with Achernar and Alpha Centauri, noting:
“Now, therefore, there are but three Stars of the first magnitude that I could perceive in all those parts which are never seene here in England. The first of these is that bright Star in the sterne of Argo which they call Canobus. The second is in the end of Eridanus. The third is in the right foote of the Centaure.”
The name Canopus is a Latinisation of the Ancient Greek name Kanôbos, recorded in Claudius Ptolemy’s Almagest (c.150 AD). Eratosthenes used the same spelling.
The name has two possible derivations, both listed in Richard Hinckley Allen’s seminal Star Names: Their Lore and Meaning.
- One from the legend of the Trojan War, where the constellation Carina was once part of the now-obsolete constellation of Argo Navis, which represented the ship used by Jason and the Argonauts. The brightest star in the constellation was given the name of a ship’s pilot from another Greek legend: Canopus, pilot of Menelaus’ ship on his quest to retrieve Helen of Troy after she was taken by Paris.
- A second from the Egyptian Coptic Kahi Nub (“Golden Earth”), which refers to how Canopus would have appeared near the horizon in ancient Egypt, reddened by atmospheric extinction from that position. A ruined ancient Egyptian port named Canopus lies near the mouth of the Nile, site of the Battle of the Nile.