Procyon

This article is about the star. For the mammalian genus to which Raccoons belong, see Procyon (genus).

Procyon A/B

The position of Procyon
Observation data Epoch J2000      Equinox J2000
Constellation	Canis Minor
Pronunciation	/ˈproʊsi.ɒn/
Right ascension	07h 39m 18.11950s
Declination	+05° 13′ 29.9552″
Apparent magnitude (V)	0.34 (A) / 10.7 (B)
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: −714.590 mas/yr Dec.: −1036.80 mas/yr
Parallax (π)	284.56 ± 1.26 mas
Distance	11.46 ± 0.05 ly (3.51 ± 0.02 pc)
Absolute magnitude (MV)	2.65/13.04
Details
Procyon A
Mass	1.42 ± 0.04 M☉
Radius	2.048 ± 0.025 R☉
Luminosity	6.93 L☉
Surface gravity (log g)	3.96
Temperature	6,530 ± 50 K
Metallicity [Fe/H]	-0.05 ± 0.03 dex
Rotation	23 days
Rotational velocity (v sin i)	3.16 ± 0.50 km/s
Age	3 Gyr
Procyon B
Mass	0.602 ± 0.015 M☉
Radius	0.01234 ± 0.00032 R☉
Luminosity	0.00055 L☉
Surface gravity (log g)	8.0
Temperature	7,740 ± 50 K
Orbit
Companion	Procyon B
Period (P)	40.82 yr
Semimajor axis (a)	1.232"
Eccentricity (e)	0.407
Inclination (i)	31.1°
Longitude of the node (Ω)	97.3°
Periastron epoch (T)	1967.97
Argument of periastron (ω) (secondary)	92.2°
Other designations
α Canis Minoris, 10 Canis Minoris, GCTP 1805.00, HR 2943, BD+05°1739, HD 61421, LHS 233, GJ 280, HIP 37279.
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 11.46 light-years (3.51 parsecs), Procyon is one of our near neighbours. Its closest neighbour is Luyten's Star, about 1.12 ly (0.34 pc) away.

Procyon forms one of the three vertices of the Winter Triangle, along with Sirius and Betelgeuse.

System

Procyon A has a stellar classification of F5IV-V. The effective surface temperature of the star is an estimated 6,530 K, giving it a white hue. It is 1.4 times the mass, twice the radius, and 6.9 times more luminous than the Sun. Procyon A is bright for its spectral class, suggesting that it is a subgiant that has nearly fused its core hydrogen into helium, after which it will 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.^{[citation needed]}

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, 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. It is 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 15.0 AUs, a little less than the distance between Uranus and the Sun, though the eccentric orbit carries them as close as 8.9 AUs and as far as 21.0 AU.

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. 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. The mass of the progenitor star for Procyon B was about 2.5 solar masses and it came to the end of its life some 1.7 ± 0.1 Gyr ago, after a main sequence lifetime of 400–600 Myr. For this reason, the age of Procyon A is expected to be at least 2 Gyr.

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. However, others argued that the non-detection was consistent with published ground-based radial velocity observations of solar-like oscillations.

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. Unlike the MOST result, the variation seen in the WIRE photometry was in agreement with radial velocity measurements from the ground.

Life

Life is unlikely around Procyon, because the habitable zone around 2.7 AU from the primary may not contain stable orbits, due to the white dwarf companion with a periastron of 8.9 AU. Also the white dwarf companion to Procyon would have stressed life severely during its red-giant phase. Procyon emits more of its light in the ultraviolet spectrum, which may be damaging to life. Still, life cannot be ruled out for other stars of the spectral type of Procyon but such life would have a relatively short time to evolve and would face heavy bombardment from comets and meteorites as happened in the first few million years of the Earth’s existence. Shortly after the phase of heavy bombardment has ended for a planet orbiting a star like Procyon the star is likely to leave the Main sequence preventing further development of life.

X-ray source

Attempts to detect X-ray emission from Procyon with nonimaging, soft X-ray sensitive detectors prior to 1975 failed. Extensive observations of Procyon were carried out with the Copernicus and TD-1A satellites in the late 1970s. The X-ray source associated with Procyon A/B was observed on April 1, 1979, with the Einstein Observatory high-resolution imager (HRI). The HRI X-ray pointlike source location is ~4" south of Procyon A, on the edge of the 90% confidence error circle, indicating identification with Procyon A rather than Procyon B which was located about 5" north of Procyon A (about 9" from the X-ray source location).

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.) In Greek mythology, Procyon is associated with Maera, a hound belonging to Erigone, daughter of Icarius of Athens. These two dog stars are referred to in the most ancient literature and were venerated by the Babylonians and the Egyptians.^{[citation needed]}

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 ghumūṣ. It is known as 南河三 (Mandarin nánhésān, the Third Star in the Southern River) in Chinese.

Procyon appears on the flag of Brazil, symbolising the state of Amazonas.

See also

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