Stellar classification



  • X -13
  • Y 4
  • Z -41
→ Sol: 43

Object type

  • Spectroscopic binary
  • Star
  • Double or multiple star
  • Infra-Red source
  • High proper-motion Star
  • Variable of RS CVn type
  • UV-emission source
  • Variable Star
  • X-ray source
simbad:* alf Aur


Capella, also designated Alpha Aurigae (α Aurigae, abbreviated Alpha Aur, α Aur), is the brightest star in the constellation of Auriga, the sixth-brightest in the night sky, and the third-brightest in the northern celestial hemisphere after Arcturus and Vega. A prominent star in the winter sky of the northern hemisphere, it is circumpolar to observers north of 44°N. Its name meaning "little goat" in Latin, Capella depicted the goat Amalthea that suckled Zeus in classical mythology. The Capella system is relatively close, at only 42.8 light-years (13.1 pc) from the Sun.

Although it appears to be a single star to the naked eye, Capella is actually a system of four stars in two binary pairs. The first pair consists of two bright yellow giant stars, both of which are around 2.5 times as massive as the Sun. They have exhausted their core hydrogen, and cooled and swollen, moving off the main sequence. Designated Capella Aa and Capella Ab, they are in a very tight circular orbit some 0.76 astronomical units (au) apart, and orbit each other every 104 days. Capella Aa is the cooler and more luminous of the two with spectral class K0III; it is 78.7 ± 4.2 times the Sun's luminosity and 11.98 ± 0.57 times its radius. An ageing red clump star, it is fusing helium to carbon and oxygen in its core. Ab is slightly smaller and hotter and of spectral class G1III; it is 72.7 ± 3.6 times as luminous as the Sun and 8.83 ± 0.33 times its radius. It is in a brief evolutionary phase known as the Hertzsprung gap as it expands and cools further to become a red giant. The Capella system is one of the brightest sources of X-rays in the sky, thought to come primarily from the corona of the more massive giant. The second pair, around 10,000 au from the first, consists of two faint, small and relatively cool red dwarfs. They are designated Capella H and Capella L. Several other stars in the same visual field have been catalogued as companions but are physically unrelated.

This article uses material from the Wikipedia article "Capella", which is released under the Creative Commons Attribution-Share-Alike License 3.0.