Canopus
What is Canopus?
Stars· Distance 310 ly · size 71× Sun. The second-brightest star in the night sky. Though 310 light-years away, it gives off about ten thousand times as much light as the Sun; it never rises from London or New York; from the southern United States or North Africa it appears only just above the southern horizon on winter nights, while from the Southern Hemisphere it rides high.
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Distance and spectral type
Canopus is about 309 light-years away, a yellow-white supergiant (spectral type F0Ib), in the constellation Centaurus. Its apparent magnitude is -0.7, visible to the naked eye.
Stellar figures
| Distance | 310 ly |
|---|---|
| Magnitude | −0.74 — second brightest star |
| Type | A9 bright giant |
| Constellation | Carina |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Behind the name
Named for Menelaus's helmsman in the Trojan War. The second-brightest star, used by spacecraft as a navigation reference.
Canopus: ten thousand Suns and an uncertain ending
The best way to grasp Canopus's brightness is to swap distances. Move Sirius, the brightest star in the night sky, out to Canopus's distance of 310 light-years and it would become a sixth-magnitude star, barely visible to the naked eye. Bring Canopus in to Sirius's distance of 8.6 light-years and it would outshine Venus by far.
Canopus appears to have used up the hydrogen in its core and to be burning helium now. It is only about 25 million years old, around a hundred-and-eightieth of the Sun's age, but heavy stars burn through their fuel quickly, so it has already reached old age. At about eight times the Sun's mass it sits right at the dividing line for exploding as a supernova, so whether it ends quietly as a heavy white dwarf or explodes is still uncertain.
The star in depth
Canopus is the brightest star in Carina, shining at magnitude −0.74. Sirius looks bright because it is close; Canopus looks bright because it truly is. It lies 310 light-years away, about 36 times farther than Sirius, yet it gives off about ten thousand times as much light as the Sun, enough to make it the second-brightest star in the sky.
Canopus is classed as a bright giant. Its radius is about 71 times the Sun's, so if it took the Sun's place it would reach almost to Mercury's orbit. Its surface is about 7,400 K, a little hotter than the Sun's. A star that is both big and hot sends out a great deal of light. Its mass is estimated at about eight times the Sun's.
Canopus also serves as a guide star for spacecraft. It is bright and lies far from the path the planets follow across the sky, so it is hard to confuse with anything else. Voyager and many other probes worked out which way they were pointing by locking onto two points: the Sun and Canopus.
Canopus sits so far south that it never rises from London or New York. From the southern United States or North Africa it appears briefly just above the southern horizon, below Sirius, on January and February nights. In ancient China and across East Asia it was called the Old Man Star, a symbol of long life, and sightings were prized. In the Sky view, switch the location to Sydney to see it riding high.
Frequently asked
- How far is Canopus from Earth?
- The distance of Canopus is 310 ly.
- How bright is Canopus (apparent magnitude)?
- The magnitude of Canopus is −0.74 — second brightest star.
- What kind of object is Canopus?
- Canopus is a A9 bright giant.
- Which constellation is Canopus in?
- Canopus lies in the constellation Centaurus.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.