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PROCYON

The eastern anchor of the Winter Triangle, Procyon is the Alpha star of Canis Minor, the smaller dog. The Greek name means "before the dog," as in northern latitudes the star rises before Sirius, the "Dog Star," and its constellation, Canis Major, and announces their quick arrival. The eighth brightest star we see in the sky, Procyon is just behind Rigel in Orion. The star is bright in part, however, because it is close to us, a mere 11 1/4 light years away, compared with Rigel's 1600 light years. By comparison, Procyon is a feeble radiator even if it is still 7 times intrinsically more luminous than the Sun. The star is an example of a "subgiant," one that is just beginning its death process, its internal core hydrogen about all burned away to helium. Procyon's chief claim to fame is a tiny companion, Procyon B, a "white dwarf" discovered in 1895, though its existence was already known from the wobbles it exerts on the brighter star, Procyon A, which were discovered in 1844. Recent Hubble Space Telescope observations show that Procyon B has a temperature of 8700 degrees above absolute zero, a bit warmer than Procyon A's 6500 degree temperature, and is only about the size of Earth. Oddly, another member of the Winter Triangle, Sirius, has a similar companion. Both are dead stars that have gone through the entire cycle of stellar evolution and now consist of highly compressed gas that is just cooling off. At one time they were mighty stars brighter than their visible companions are today.