Canopus is a brilliant star in the southern constellation of Carina and the second brightest in the night sky. At magnitude -0.72, it's about half as bright as Sirius but appearances can be deceptive; Canopus is far the more powerful star and Sirius only appears brighter because it's much closer to us. With a declination of -52 degrees, Canopus is best seen from southern latitudes. It can appear high in the sky from Australia, New Zealand, South Africa and much of South America. Indeed from such locations, the star is either circumpolar or only sets briefly.
Canopus can't be seen from most of Europe and many parts of the United States. For observers north of 38 degrees latitude, it never rises above the horizon. However, those living in southern Spain, southern Portugal, southern Florida, southern Texas and Hawaii can glimpse the star during the winter months. It's also visible from India, Pakistan and much of China and Japan.
From a historical perspective, Canopus can be seen from Alexandria but not from Athens. This provided early proof that the Earth is a globe and not a flat disk.
Canopus is of the course the primary star in Carina. In previous times, this area of sky was part of much larger Argo Navis, a constellation named after the ship that carried Jason and the Argonauts in their quest for the Golden Fleece. Argo Navis was the largest constellation in the sky and considerably larger than today's titleholder, Hydra. Canopus traditionally marked the rudder of the ship, but Argo Navis was such an unwieldy grouping that the International Astronomical Union (IAU) eventually lost patience and chopped it up into Carina (a keel), Puppis (a poop), Vela (sails) and Pyxis (a compass). French astronomer, Lacaille, had earlier proposed the separate parts. Eventually they were accepted by the IAU, along with the dropping of the Argo name.
In ancient times, Canopus was a star of great importance, although the origin of its name is unclear. One possibility, is the legendary captain of the ship in the Trojan War that carried King Menelaus home after the fall of Troy. While landing in Egypt, the captain failed to survive an encounter with a snake and Menelaus built a monument in his honour with a town growing up around it. Eventually, the town fell into ruins. The site today is occupied by the city of Aboukir. Another theory is that Canopus comes from the Egyptian meaning "Golden Earth", a possible reference to its appearance when battling against the thick atmospheric haze above the Egyptian horizon.
Arab nomads respected greatly the star. When rising in the dawn sky for the first time each year, it signalled summer was over and time for weaning the camels. The New Zealand Maori's used sightings of Canopus to plant crops. Today, astronauts and space probes often use Canopus for navigational purposes.
The star itself is a type F0Ib supergiant and therefore should have a yellowish tinge, but most observers report it as pure white. The surface temperature is 7,350K and considerably hotter than the 5,778K of the Sun. It's also 14,500x more luminous than our star. At a distance of 310 light-years and with an absolute magnitude of -5.6, Canopus is the most intrinsically bright star within 700 light-years. Currently there is no bright star near the southern pole but around 14,000 AD the effects of precession will take Canopus to within 10 degrees of it.
Canopus is located south of Sirius, not that you will need a marker to find it. It dominates the surrounding area of sky, but has not always done so. The erratic variable star, Eta Carinae, in the mid 19th century outshone Canopus and almost rivalled Sirius. It may well return to such brilliance, but for now, Canopus reigns supreme in this region of sky.
Canopus Data Table
|Bayer||alpha (α) Car|
|RA (J2000)||06h 23m 57s|
|DEC (J2000)||-52d 41m 44s|
|Surface Temp (K).||7,350|
|Age (years)||~10 Million|
|Other designations||Suhail, HR 2326, HD 45348, HIP 30438|
|Notable feature||Second brightest star in the night sky|