Procyon

Procyon (α CMi, α Canis Minoris, Alpha Canis Minoris) is the brightest star in the constellation Canis Minor."Procyon". Oxford English Dictionary. Oxford University Press. 2nd ed, 1989. 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.Kervella P. et al 2004."The diameter and evolutionary state of Procyon A. Multi-technique modeling using asteroseismic and interferometric constraints. Astronomy and Astrophysics 413 (1): 251–256. 

It is actually a binary star system 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,Provencal J.L. et al 2002. Procyon B: outside the iron box. The Astrophysical Journal 568 (1): 324–334.  named Procyon B.

The reason for its brightness is not its intrinsic luminosity but its relative closeness to the Sun. Its distance was worked out by the European Space Agency Hipparcos astrometry satellite.Perryman M.A.C. et al 1997. The Hipparcos Catalogue. Astronomy and Astrophysics 323: L49–L52Perryman, Michael 2010. The making of history's greatest star map. Heidelberg: Springer-Verlag. It is just  away,van Leeuwen F. 2007. Validation of the new Hipparcos reduction. Astronomy and Astrophysics 474 (2): 653–664.  and is one of our nearest stellar neighbours. Its closest neighbour is Luyten's Star, about  away.

Procyon forms one of the three vertices of the Winter Triangle, along with Sirius and Betelgeuse. Its colour index is 0.42, and its hue has been described as having a faint yellow tinge to it.Schaaf, Fred 2008. The brightest stars: discovering the universe through the sky's most brilliant stars. Hoboken, New Jersey: John Wiley, 166. 

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Category:Binary stars