Canopus
Canopus — the second-brightest star in the night sky after Sirius, and the brightest in the far-southern constellation Carina, about 310 light-years away. A yellow-white supergiant roughly 71 times the Sun's diameter and one of the most luminous stars in the solar neighbourhood, it shines so steadily and sits so far from the ecliptic that spacecraft from Mariner onward have used dedicated 'Canopus trackers' to lock onto it and fix their orientation in deep space.
Key facts
Science
Physical
- Mass
- 1.59 × 10³¹ kg · 8 M☉
- Radius
- 0.33 AU · 71× wider than the Sun
- Density
- 0.0315 kg/m³ · 3.2e-05× water
- Spectral type
- A9 II (yellow-white bright giant)
Composition
- By mass
- A yellow-white supergiant about 71 times the Sun's radius — from its interferometric angular diameter (Domiciano de Souza et al. 2008) and the Hipparcos distance — and far more luminous than the Sun. At roughly 8 solar masses it has left the main sequence and is fusing helium in its core; it is expected to end not as a supernova but as a rare, massive neon–oxygen white dwarf. Its steadiness and brightness make it the standard reference star for spacecraft attitude sensors, from the 1960s Mariners onward.
Temperature
- Surface
- 7,400 K (7127 °C)
Radiation & temperature
- Surface temperature
- 7,400 K (7127 °C)
- Peak wavelength
- 392 nm · violet-blue light
Discovery & history
- Method
- Naked-eye star
- Name
- 'Canopus' — after the mythical pilot of the Spartan king Menelaus's ship; Alpha Carinae, the brightest star of Carina, the Keel.
Known since antiquity — a guiding star for ancient Egyptian, Greek, Arab and Polynesian navigators alike, and named for the helmsman of the Greek fleet at Troy. Its steady brightness later made it the reference star of choice for interplanetary probes, which have carried star trackers pointed at Canopus since the 1960s Mariners.
Images
Images from open archives · credit shown per image