PROCYON (Alpha Canis Minoris), brightest star in the constellation Canis Minor. Procyon is a yellow-white main sequence star, twice the size and 7 times more luminous than the Sun. It's the fifth brightest star in the sky, but like Alpha Centauri it appears so bright only because at 11.4 light-years, it is relatively close.
Procyon is an example of a main sequence "subgiant" star, one that is beginning the death process by converting its remaining core hydrogen into helium. Procyon is currently twice the diameter of the Sun, one of the largest stars within 20 light-years.
Procyon is orbited by a white dwarf companion detected visually in 1896 by John M. Schaeberle. The fainter companion's existence was first noted in 1840, however, by Arthur von Auswers who observed irregularities in Procyon's proper motion best explained by a massive albeit faint companion. At just one-third the size of Earth, the companion dubbed Procyon B contains 60 percent of the Sun’s mass. The brighter component is now known as Procyon A. 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.
The word Procyon is Greek for 'Before the Dog', for the reason that in the Northern Hemisphere, Procyon announces the rise of Sirius, the Dog Star.
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