Last modified on 10 January 2018, at 08:07


Position Alpha Cmi.png
Observational Data
Designation Alpha Canis Minoris
Right ascension 07h 39m 18.1/17.7s
Declination 05o 13' 29/20"
Constellation Canis Minor
Type of object Binary star
Magnitude Apparent Mag: 0.34(A) 10.7(B)
Absolute Mag: 2.65(A) 13.04(B)
Distance from Earth 11.4 ly
Radial velocity −3.2 km/s
Proper motion RA: −716.57 mas/yr
Dec.: −1034.58 mas/yr
Parallax 286.05 ± 0.81 mas

Procyon, also known as Alpha Canis Minoris or the Little Dog Star, is the brighter of the 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 the primary star Procyon A and its white dwarf companion, Procyon B. The primary star has an apparent magnitude of 0.34, allowing for it to be easily seen in the night sky. This is due more to its relative closeness then anything else, as the star is only 11.41 light years away.

Procyon is also part of the Winter Triangle along with Betelgeuse and Sirius.

Procyon 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, equivalent to 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 observances of 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.[1]

Procyon A

Procyon A is the eighth brightest star in the night sky, and with an apparent magnitude of 0.34, can easily be seen in all but the most light polluted skies. The star itself is a white-yellow, main sequence dwarf of spectral type F5 V-IV. Procyon is some 1.5 times the mass of the Sun,[2] and some 1.4 to 2.3 times the diameter. Procyon A is also 7.5 times as bright as our Sun.[3]

The metallicity of Procyon A is around 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 puffed out its metals-rich outer layers before becoming a white dwarf.[4]

The star is also a BY Draconis-type variable star. Although its brightness does change from the point of the observer because of eclipsing by Procyon B, the star varies intrinsically as well. It has a New Suspect Variable (NVS) designation of NVS 3672.

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 to be around 15,000 times fainter then its primary. Procyon B is also only 6/10,000th as luminous as our Sun, and only 2 perfect its 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.[5]

Substellar Companions

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