Definitions

Procyon

Procyon

[proh-see-on]
Procyon, brightest star in the constellation Canis Minor; Bayer designation α Canis Minoris; 1992 position R.A. 7h38.9m, Dec.+5°15'. A yellow-white star of spectral class F5 IV-V, it is one of the nearer bright stars, lying about 11.5 light-years away. Its name is from the Greek meaning "before the dog," i.e., before the Dog Star, Sirius, the brightest star in the sky. Procyon is a brilliant star in its own right, its apparent magnitude of 0.35 making it one of the 10 brightest stars in the sky. It is a visual binary star.
or ringtail

North American raccoon (Procyon lotor).

Any of seven species of omnivorous, nocturnal carnivores (genus Procyon, family Procyonidae) characterized by a bushy, ringed tail and a black mask on the face. The North American raccoon (P. lotor) has a stout body, short legs, pointed muzzle, and small erect ears. It is 30–36 in. (75–90 cm) long, including the 10-in. (25-cm) tail, and weighs over 22 lb (10 kg). The shaggy, coarse fur is iron-gray to blackish. The feet resemble slender human hands. Raccoons eat arthropods, rodents, frogs, berries, fruit, and plants; in towns and cities they thrive on garbage. They prefer woods near water and usually live in hollow trees. The crab-eating raccoon (P. cancrivorus) of South America is similar but has coarser fur.

Learn more about raccoon with a free trial on Britannica.com.

This article is about the star. Procyon is also the mammalian genus to which raccoons belong.
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 eighth 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.,,. 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; though its orbit was known as far back as 1861, it was not visually confirmed until 1896. 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.

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 ~8600 km, versus ~5800 km for Sirius B., With a surface temperature of 7740 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. 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.

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.

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

References

See also

External links

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