Procyon (α CMi / α Canis Minoris / Alpha Canis Minoris) is the brightest star in the constellation Canis Minor and the eighth brightest star in the nighttime sky.
Its name comes from the Greek προκύον (prokúon), meaning "before the dog", since it precedes the "Dog Star" Sirius as it travels across the sky due to Earth's rotation. (Although Procyon has a greater right ascension, it also has a more northerly declination, which means it will rise above the horizon earlier than Sirius from most northerly latitudes.) These two dog stars are referred to in the most ancient literature and were venerated by the Babylonians and the Egyptians.
Procyon is a vertex of the Winter Triangle.
Procyon is one of the closest stars to Earth's solar system, being only 3.5 pc or 11.41 light years away. Like Sirius, it is a binary star —the main star (Procyon A) having a faint white dwarf companion (Procyon B). Its closest neighbour is Luyten's star, 0.34 pc or 1.11 ly away.
Procyon A is a yellowish-white star somewhat larger and 7.5 times brighter than the Sun, of spectral type F. In fact, because it is bright even for its spectral class, it is thought to be a subgiant, meaning it has just finished fusing its hydrogen into helium and begun to expand. So far, it is not thought that the star has begun to "redden" but as it continues to expand, the star will swell to about 80 - 150 times its current diameter and become a red or orange color. This will probably happen within 10 - 100 million years. It is expected that the Sun will also go through this process when it begins to die.
In late June of 2004, Canada's orbital MOST satellite telescope completed a 32-day survey of Procyon A. The continuous optical monitoring was intended to confirm oscillations in its brightness observed from Earth. During the entire two month period however, no fluctuation in intensity whatsoever was observed. These findings have caused astrophysicists to question the accepted tenets of helioseismology, and theories of star formation.
Canis Minor constellation | Binary stars | Bayer objects | HD and HDE objects | White dwarfs | Yellow-white dwarfs | Yellow-white subgiants
Procyon | Prokyon | Procyon (estrella) | Procyon (étoile) | Procione (astronomia) | Prokyonas | Procyon (ster) | プロキオン | Procjon | Procyon (estrela) | Процион | Prokyón | Procyon | Procyon | 南河三