mardi 23 septembre 2008

Canis Minor 5

Procyon (α CMi / α Canis Minoris / Alpha Canis Minoris) is the brightest star in the constellation 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 actually 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 DA, named Procyon B. The reason for its brightness is not its intrinsic luminosity but its closeness to the Sun; at a distance of 3.5 pc or 11.41 light years, Procyon is one of our near neighbours. Its closest neighbour is Luyten's star, 0.34 pc or 1.11 ly away.
Procyon forms one of the three vertices of the Winter Triangle, along with Sirius and Betelgeuse.

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.
It is known as 南河三 (Nánhésān, the Third Star in the Southern River) in Chinese.

Beta Canis Minoris (β CMi / β Canis Minoris) is a star in the constellation of Canis Minor. It also has the traditional name Gomeisa.
Beta Canis Minoris is a hot, B8-class main sequence star of apparent magnitude 2.9, easily visible to the naked eye. It is slightly variable, and belongs to the Gamma Cassiopeiae category of variable stars. This star is rotating rapidly and is surrounded by a disk of material, which the emissions are heating up.
The traditional name is supposed to be from an Arabic word al-ghumaisa’ "the bleary-eyed one", cognate with the modern Arabic name for Procyon, غموص ghumūş.

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