Procyon (UK: PROH-see-on), also designated Alpha Canis Minoris (α Canis Minoris, abbreviated Alpha CMi, α CMi), is the brightest star in the constellation of Canis Minor; to the naked eye, it appears to be a single star, the eighth-brightest in the night sky with a visual apparent magnitude of 0.34. It is a binary star system, consisting of a white main-sequence star of spectral type F5 IV–V, named Procyon A, and a faint white dwarf companion of spectral type DQZ, named Procyon B.
As determined by the European Space Agency Hipparcos astrometry satellite, it lies at a distance of just 11.46 light -years (3.51 parsecs), and is therefore one of Earth 's nearest stellar neighbours.
Visibility
Procyon is the eighth-brightest star in the night sky, culminating at midnight on January 14. It forms one of the three vertices of the Winter Triangle asterism, in combination with Sirius and Betelgeuse. The prime period for evening viewing of Procyon is in late winter in the northern hemisphere.It has a color index of 0.42, and its hue has been described as having a faint yellow tinge to it.
System
Procyon is a binary star system with a bright primary component, Procyon A, having an apparent magnitude of 0.34, and a faint companion, Procyon B, at magnitude 10.7. The pair orbit each other with a period of 40.82 years along an elliptical orbit with an eccentricity of 0.407. The plane of their orbit is inclined at an angle of 31.1° to the line of sight with the Earth. The average separation of the two components is 15.0 AU, a little less than the distance between Uranus and the Sun, though the eccentric orbit carries them as close as 8.9 AU and as far as 21.0 AU.
Primary star
The primary has a stellar classification of F5IV–V, indicating that it is a late-stage F-type main-sequence star. Procyon A is bright for its spectral class, suggesting that it is evolving into a subgiant that has nearly fused its core hydrogen into helium, after which it will expand as the nuclear reactions move outside the core.
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