Canopus is the brightest star in the southern constellation of Carina, and the second-brightest star in the night sky after Sirius. Though the star is so bright, it is not visible from all across the globe due to Earth’s movement.
Key Facts & Summary
- Canopus is at around 310 light-years / 95 parsecs away from the Sun. It is located on the western edge of the Carina constellation.
- Though it is the second-brightest star in the night sky, it is almost two times fainter than Sirius, the brightest star, because of its distance.
- Canopus has an apparent visual magnitude of – 0.74 and an absolute magnitude of – 5.71.
- Canopus is an aging bright giant of spectral type A9 or F0, it appears white to the naked eye.
- Canopus is eight times more massive than our Sun and has expanded up to 71 times the Sun’s radius.
- Canopus is more than 10.000 times brighter than our sun, and its enlarged photosphere has a temperature of around 7.000 K. It is emitting X-rays, most likely from its corona.
- The star is currently undergoing core helium burning while it is in the so-called blue loop phase of its evolution. Canopus has already passed through the red-giant branch after exhausting its hydrogen supplies at its core.
- Canopus has a rotational velocity of around 8 km / 4 mi per second
- The name, Canopus, was first recorded in Ptolemy’s Almagest in 150 A.D.
- Many observers in the southern hemispheres can see Canopus and Sirius reach the meridian at around 21 minutes apart from each other. They can both be seen at the same time in the sky.
- The star can’t be seen from most locations in Europe and North America.
- Canopus culminates on February 11th, at around 9 pm, and at midnight on December 27.
- Canopus made its closest approach to the Sun at around 3.1 million years ago. It came within 172 light-years from us.
Since it is the second-brightest star in the night sky, Canopus inevitably ended up in multiple myths, gained religious importance, and was associated with many things for numerous civilizations and cultures.
While the historical development of the name “Canopus” is well documented, its exact origin is uncertain. The most widely accepted theory is that the star was named after the pilot of a ship which Menelaus, the king of Mycenean (pre-Dorian) Sparta, sailed to retrieve his wife Helen of Troy after she was kidnapped by Paris.
When they arrived, Canopus was bitten by a snake and quickly died. Menelaus wanted to honor him and named a port there after him. When he was giving his dedicatory speech, a bright star rose in the sky and Menelaus decided to name this star after Canopus as well.
This ancient port now lais in ruins, but the village of Al Bekur (Aboukir), which occupies its site, is also known in history as the site of Lord Nelson’s Battle of the Nile – 1789.
Another hypothesis regarding the name suggests that Canopus is derived from the Egyptian words Kahi Nub, which translates to “Golden Earth.” For the ancient Egyptians, the star would have appeared near the horizon and thus it may have had a reddish color because the observers would see it through a thicker layer of atmosphere.
Canopus formed millions of years ago from molecular clouds in the vicinity of the Scorpius-Centaurus association. Its exact age is unknown. Gravity pulled swirling gas and dust together and thus formed the second-brightest star in the night sky that we now call Canopus – Alpha Carinae. It is quite possible that this star is relatively young.
Distance, Size, and Mass
Canopus is at around 310 light-years / 95 parsecs away from the Sun. It is a gigantic star with a diameter of around 98.789 million km / 61.384 million mi – around 50 times bigger than Sirius’s diameter.
Compared to the sun’s diameter, Canopus is around 75 times bigger. Along with this, Canopus is eight times more massive than our Sun and has expanded up to 71 times the Sun’s radius.
Though Canopus is more than 10.700 times brighter than our sun, it is two times fainter than Sirius, the brightest star in the night sky, because it is much far away. Canopus is actually the most intrinsically bright star within 700 light-years away from the solar system. Its average surface temperature is at around 7.000 K, much hotter than our sun with more than 1.000 Kelvins.
When it comes to the star’s corona, it is heated at around 15 million K – around 7.5 times the heat of the sun’s corona. It is thought that because of this, Canopus is a strong source of X-rays.
Canopus’s projected orbit takes it between 21.300 to 24.300 light-years from the galaxy’s center.
Canopus is located in the constellation of Carina, marking the western edge of the constellation. Though Canopus wasn’t visible to the ancient Greeks and Romans, the constellation of Carina was.
It was part of a larger constellation called the Argo Navis – this constellation represented the ship of Jason and the Argonauts. Canopus marked the ship’s keel.
Though Canopus was the brightest star of Argo Navis, the constellation was later divided into three lesser constellations: Carina – the keel – Puppis – the stern – and Vela – the sails.
Though Canopus is much bigger than our Sun, it is not large enough to end its life in a supernova explosion. The star will most likely end up becoming a white dwarf after much of its mass will be expelled to form a planetary nebula.
Did you know?
- Canopus is a member of the Scorpius-Centaurus Association, the nearest OB association to the solar system. Antares, most of the stars that form the Southern Cross, and a number of other bright stars in the constellations of Lupus, Crux, Centaurus, and Scorpius, are part of this.
- If Canopus would be placed in the center of our solar system, the star’s surface would extend to about 90% of the distance from the Sun to Mercury, and it would have an apparent magnitude of -37.
- The flag of Brazil features 27 stars with each and every one of them symbolizing a Brazilian Federative Unit. Canopus is one of these stars and it represents the state of Goias.
- In Dante’s Purgatorio – Canopus along with Achernar and Fomalhaut made up the Tre Facelle symbolizing Faith, Hope, and charity.
- The Kalapalo people in Brazil considered Canopus, Procyon, Castor, and Pollux to make up the asterism known as the celestial Duck.
- Since the star is so bright, it was used by many civilizations for navigation. For the ancient Polynesians for example, the star marked the southern wingtip of a constellation they knew as the Great Bird or Manu.
- Canopus was associated with Agastya – one of the ancient sages of rishis in the Indian literature.
- In Japana and China, Canopus was known as the Old Man star.