Canopus
Canopus is the brightest star in the southern constellation of Carina and the second-brightest star in the night sky. It is also designated α Carinae, which is romanized (transliterated) to Alpha Carinae. With a visual apparent magnitude of −0.74, it is outshone only by Sirius.
An image of Canopus by Expedition 6 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Carina |
| Pronunciation | /kəˈnoʊpəs/ |
| Right ascension | 06h 23m 57.10988s |
| Declination | −52° 41′ 44.3810″ |
| Apparent magnitude (V) | −0.74 |
| Characteristics | |
| Spectral type | A9 II |
| U−B color index | +0.10 |
| B−V color index | +0.15 |
| Astrometry | |
| Radial velocity (Rv) | 20.3±0.5 km/s |
| Proper motion (μ) | RA: 19.93 mas/yr Dec.: 23.24 mas/yr |
| Parallax (π) | 10.55 ± 0.56 mas |
| Distance | 310 ± 20 ly (95 ± 5 pc) |
| Absolute magnitude (MV) | –5.71 |
| Details | |
| Mass | 8.0±0.3 (2013) 10.1±0.1 (2011) 9.81±1.83 (2021) M☉ |
| Radius | 71±4 (2013) 73.3±5.2 (2021) R☉ |
| Luminosity | 10,700 L☉ |
| Surface gravity (log g) | 1.70±0.05 cgs |
| Temperature | 7,400 K |
| Metallicity [Fe/H] | –0.07 dex |
| Rotation | ≥298 d |
| Rotational velocity (v sin i) | 9 km/s |
| Age | 25.1±2.5 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Located around 310 light-years from the Sun, Canopus is a bright giant of spectral type A9, so it is essentially white when seen with the naked eye. It has a luminosity over 10,000 times the luminosity of the Sun, is eight times as massive, and has expanded to 71 times the Sun's radius. Its enlarged photosphere has an effective temperature of around 7400 K. 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 is a source of X-rays, which are likely being emitted from its corona.
The prominent appearance of Canopus means it has been the subject of mythological lore among many ancient peoples. Its proper name is generally considered to originate from the mythological Canopus, who was a navigator for Menelaus, king of Sparta. The acronycal rising marked the date of the Ptolemaia festival in Egypt. In ancient India, it was named Agastya after the revered Vedic sage. For Chinese astronomers, it was known as the Old Man of the South Pole.