Canopus (Alpha Carinae)
Canopus (Alpha Carinae) is a star in the constellation Carina, magnitude -0.7.
The second-brightest star in the sky — a white bright giant named after a legendary ship’s pilot.
Canopus is a star in a late, restless stage of life. It has used up the hydrogen in its core, swollen to about 71 times the Sun’s width, and now burns helium instead. Nine or ten times the Sun’s mass, it shines with more than 10,000 times the Sun’s light from a surface at about 7,400 K — hot enough to look white.
Sirius only beats it because Sirius is so close to us. Over the past four million years Canopus has been the brightest star in our sky three times, and in about 480,000 years, once Sirius has drifted away, it will take the crown back for around 510,000 years.
Its name honours Canopus, the pilot of King Menelaus’s ship on the voyage to recover Helen of Troy — fitting for the leading star of the great ship Argo Navis, where it marked the steering oar. In India it is Agastya, after a revered sage. Chinese astronomers called it the Old Man of the South Pole, and in Arabic it is Suhail.
Canopus (Alpha Carinae) is 310 light-years away: the light we see from it set off around 1715, 30 years after Isaac Newton published his laws of motion and gravity.
Did you know?
- A star that proved the Earth is round. In 1153 the scholar Ibn Rushd travelled from Córdoba to Marrakesh to see Canopus, which never rose at home. He used the way its visibility changes with latitude to argue that the Earth is a sphere.
- Never seen from England. In 1592 the explorer Robert Hues listed Canopus as one of only three first-magnitude stars he had seen on his voyages that can never be seen from England. The others were Achernar and Alpha Centauri.
- A rare sight. Seen only rarely from Middle Eastern latitudes, Canopus gave its Arabic name, Suhail, a second meaning: something seldom seen.
A brilliant white star, second in brightness only to Sirius, which it accompanies across the sky. It never rises north of about latitude 37° N. Near the horizon it can look yellow or even reddened — compare it with Sirius when both are high.
When and where to see it
It is best placed in the evening sky around January, when it crosses the meridian at about 10 pm local time (around midnight in December). It can be seen from everywhere south of 37°N and never sets south of 37°S.
At its highest it stands below the horizon from 50°N, 2° up from 35°N, 37° up from the equator, 72° up from 35°S.
Facts
- Type
- Star
- Constellation
- Carina
- Designations
- Alpha Carinae, α Car, HR 2326, HD 45348, HIP 30438
- Magnitude
- -0.7
- Position
- RA 6h 24.0m, Dec −52° 42′ (J2000)
- Spectral type
- A9II
- Colour
- yellow-white (B−V 0.15)
- Distance
- 310 light-years
- Discovered
- Known since antiquity
Open AstroPilot to see when Canopus (Alpha Carinae) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view.