Procyon

Procyon A/B

The position of Procyon.
Observation data Epoch J2000      Equinox J2000
Constellation	Canis Minor
Pronunciation	/ˈproʊsi.ɒn/
Right ascension	07h 39m 18.1/17.7s
Declination	+05° 13' 29/20"
Apparent magnitude (V)	0.34/10.7
Characteristics
Spectral type	F5 IV-V/DA
U-B color index	−0.01
B-V color index	0.40/0.0
Astrometry
Radial velocity (Rv)	−3.2 km/s
Proper motion (μ)	RA: −716.57 mas/yr Dec.: −1034.58 mas/yr
Parallax (π)	286.05 ± 0.81 mas
Distance	11.4 ± 0.03 ly (3.496 ± 0.01 pc)
Absolute magnitude (MV)	2.65/13.04
Details
Procyon A
Mass	1.50 M☉
Radius	2.05 R☉
Surface gravity (log g)	4.0
Luminosity	7.73 L☉
Temperature	6,650 K
Metallicity	110% Sun
Age	3 × 109[1] years
Procyon B
Mass	0.602 ± 0.015[1] M☉
Radius	0.01234 ± 0.00032[1] R☉
Surface gravity (log g)	8.0[1]
Luminosity	0.00055 L☉
Temperature	7,740 ± 50[1] K
Orbit
Companion	Procyon A
Period (P)	40.82 yr
Semimajor axis (a)	4.27"
Eccentricity (e)	0.41
Inclination (i)	31.9°
Longitude of the node (Ω)	284.8°
Periastron epoch (T)	1967.86
Other designations
α Canis Minoris, 10 Canis Minoris, GCTP 1805.00, HR 2943, BD+05°1739, HD 61421, LHS 233, GJ 280, HIP 37279, GC 10277, ADS 6251, CCDM 07393+0514, TD1 10647.
Database references
SIMBAD	data

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 seventh 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.

System

Procyon A is a white star of spectral type F5; it is 1.4 times the mass, twice the diameter, and 7.5 times more luminous than the Sun.^[2][3][4] It is bright for its spectral class, suggesting that it is a subgiant that has completely fused its core hydrogen into helium, and begun to expand as "burning" moves outside the core. As it continues to expand, the star will eventually swell to about 80 to 150 times its current diameter and become a red or orange color. This will probably happen within 10 to 100 million years. It is expected that the Sun will also go through this process when hydrogen fusion ceases at its core.

Like Sirius B, Procyon's companion is a white dwarf that was inferred from astrometric data long before it was observed. Its existence had been postulated by Friedrich Bessel as early as 1844, and although its orbital elements had been calculated by Arthur Auwers in 1862 as part of his thesis^[5], Procyon B was not visually confirmed until 1896 when John Martin Schaeberle observed it at the predicted position using the 36-inch refractor at Lick Observatory.^[6] It is even more difficult to observe from Earth than Sirius B, due to a greater apparent magnitude difference and smaller angular separation from its primary. The average separation of the two components is 15 AUs, a little less than the distance between Uranus and the Sun, though the eccentric orbit carries them as close as 9 AUs and as far as 21.^[4]

At 0.6 solar masses, Procyon B is considerably less massive than Sirius B; however, the peculiarities of degenerate matter ensure that it is larger than its more famous neighbor, with an estimated radius of ~8,600 km, versus ~5,800 km for Sirius B.^[1][7] With a surface temperature of 7,740 K, it is also much cooler than Sirius B; this is a testament to its lesser mass and greater age.

Oscillations controversy

In late June 2004, Canada's orbital MOST satellite telescope carried out a 32-day survey of Procyon A. The continuous optical monitoring was intended to confirm solar-like oscillations in its brightness observed from Earth and to permit asteroseismology. No oscillations were detected and the authors concluded that the theory of stellar oscillations may need to be reconsidered.^[8] However others argued that the non-detection was consistent with published ground-based radial velocity observations of solar-like oscillations.^[9][10]

Photometric measurements from the NASA Wide Field Infrared Explorer (WIRE) satellite from 1999 and 2000 showed evidence of granulation (convection near the surface of the star) and solar-like oscillations.^[11] Unlike the MOST result, the variation seen in the WIRE photometry was in agreement with radial velocity measurements from the ground.

Etymology and cultural significance

Its name comes from the Greek προκύον (prokyon), 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.

Rarer names are the Latin translation of Procyon, Antecanis, and the Arabic-derived names Al Shira and Elgomaisa. The first derives from الشعرى الشامية aš-ši‘ra aš-šamiyah "the Syrian sign" (the other sign being Sirius; "Syria" is supposedly a reference to its northern location relative to Sirius); the second from الغميصاء al-ghumaisa’ "the bleary-eyed (woman)", in contrast to العبور "the teary-eyed (woman)", which is Sirius. (See Gomeisa.) The modern Arabic name for Procyon is غموص ghumūş. It is known as 南河三 (Mandarin nánhésān, the Third Star in the Southern River) in Chinese.

See also

• List of brightest stars
• List of nearest stars
• Procyon in astrology
• Procyon in fiction

References

External links

• Sol Station — Procyon

Coordinates: 07^h 39^m 18.1^s, +05° 13′ 29″