Procyon

Procyon, also known as Alpha Canis Minoris or the Little Dog Star, is the brighter of two stars that make up the constellation Canis Minor. Although appearing as a single star to the unaided eye, Procyon is actually a binary system made up of an F5 star Procyon A and it's white dwarf companion, Procyon B. The star has an apparent magnitude of 0.34, allowing for it to be easily seen in the night sky, this is due more to it's relative closeness then anything else as the star is only 11.41 light years away.

Procyon is also part of the Winter Triangle, which it makes up along with Betelgeuse and Sirius.

Star in History

Unlike many modern star names that are Arabic in origin, Procyon comes from the Greek προκύον, meaning "before the dog" as Procyon rises before and preceded Sirius, the "Dog Star" in the night sky as the Earth rotates.

The original Arabic name for Procyon is Al Shira, from the phrase الشعرى الشامية aš-ši‘ra aš-šamiyah, translated as "the Syrian sign". In Latin, the star was called Antecanis, while in China it is referred to as 南河三 (nánhésān, or "Third Star in the Southern River").

Star System

The two stars of the Procyon system orbit each other with an average distance of 14.9 AU, or the distance of Uranus from the Sun, although the orbit is eccentric and carries the two stars as close as 9 AU and as far as 21 AU. The secondary or companion star, Procyon B isn't visible to the unaided eye and wasn't postulated to exist until 1840 through the irregularities in the proper motion of the Procyon system. Procyon B was first visually confirmed with a 36 inch refracting telescope in 1896 by John M. Schaeberle.

Procyon A

Procyon A is the eight brightest star in the night sky, and with it's 0.34 magnitude, can easily be seen in all but the most light polluted skies. The star is a white-yellow, main sequence dwarf of spectral type F5 V-IV. Procyon is some 1.5 times to mass of the Sun, and some 1.4 to 2.3 times the diameter. Procyon A is also some 7.5 times as bright as out Sun.

The metallicity of Procyon A is some 1.4 times that of the Sun, based on its abundance of iron. It is theorized that Procyon A is metal-rich because it was enriched by Procyon B when the latter lost puffed out it's metals-rich outer layers before becoming a white dwarf.

Procyon A is a relatively young star that is only some 1.7 billion years old. Because of the fact Procyon is much hotter and larger then our Sun, it will exhaust it's hydrogen fuel in the core within a few billion years and evolve into a red giant before losing it's outer layers and become a white dwarf much like it's companion.

Procyon B

Procyon B is a dim white dwarf of spectral class DQZ, A4, however the close proximity to the much brighter Procyon A has made precise measurements about the star's spectrum difficult. The star is estimated though to be around 15,000 times fainter then it's primary. Procyon B is also only 6/10,000th as luminous as our Sun, and only 2 perfect it's diameter. Because it is a white dwarf, it still has 60 percent of our Sun's mass, having a density estimated to be over two tones per cubic inch.

Substellar Companions

So far there is no supporting evidence for a substellar companion around either star. the habitable zone for Procyon A is centered around 2.7 AUs where liquid water could exist on an Earth-like world.