Procyon
From Wikipedia, the free encyclopedia
- This article is about the star. Procyon is also the mammalian genus to which Raccoons belong.
 The position of Procyon. |
|
| Observation data Equinox J2000 |
|
|---|---|
| Constellation | Canis Minor |
| 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 |
| Variable type | ? |
| 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 | |
| Mass | 1.50/0.60 M☉ |
| Radius | 1.86/0.02 R☉ |
| Luminosity | 7.73/0.00055 L☉ |
| Temperature | 6,650/9,700 K |
| Metallicity | 110% Sun |
| Rotation | |
| Age | 1.7 × 109 years |
| Visual binary orbit | |
| Companion | Procyon B |
| Period (P) | 40.82 a |
| Semimajor axis (a) | 1.18" |
| Eccentricity (e) | 0.36 |
| Inclination (i) | 31.9° |
| Node (Ω) | 284.8° |
| Periastron epoch (T) | 1967.86 |
| Other designations | |
| Database references | |
| SIMBAD | data |
Procyon (α CMi / α Canis Minoris / Alpha Canis Minoris) is the brightest star in the constellation Canis Minor and the eighth brightest star in the nighttime sky.
Its name comes from the Greek προκύον (prokúon), 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.
Procyon is a vertex of the Winter Triangle.
Procyon is one of the closest stars to Earth's solar system, being only 3.5 pc or 11.41 light years away. Like Sirius, it is a binary star —the main star (Procyon A) having a faint white dwarf companion (Procyon B). Its closest neighbour is Luyten's star, 0.34 pc or 1.11 ly away.
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[edit] Procyon A
Procyon A is a yellowish-white star of spectral type F; it is 1.4 times the mass, twice the diameter, and 7.5 times more luminous than the Sun.[1],[2],[3]. 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 - 150 times its current diameter and become a red or orange color. This will probably happen within 10 - 100 million years. It is expected that the Sun will also go through this process when it begins to die.
[edit] Oscillations controversy
In late June of 2004, Canada's orbital MOST satellite telescope completed a 32-day survey of Procyon A. The continuous optical monitoring was intended to confirm oscillations in its brightness observed from Earth and to permit asteroseismology but no oscillations were detected.
However, 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.
[edit] Procyon B
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.[4] It is even more difficult to observe from Earth than Sirius B, due to a greater 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.[5]
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.[6],[7] 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.[8]
[edit] Footnotes
- ^ Gatewood G. and Han I., "An astrometric study of Procyon". Astron. J., 131, 1015-1021 (2006) - February 2006. http://simbad3.u-strasbg.fr/cgi-bin/cdsbib4?2006AJ....131.1015G Accessed 2/3/07.
- ^ Astron. Astrophys., 413, 251-256 (2004) - January(I) 2004 Kervella et al., "The diameter and evolutionary state of Procyon A. Multi-technique modeling using asteroseismic and interferometric constraints". Astron. Astrophys., 413, 251-256 (2004) - January(I) 2004 http://simbad3.u-strasbg.fr/cgi-bin/cdsbib4?2004A%26A...413..251K Accessed 2/3/07.
- ^ Solstation.com, "Procyon 2". http://www.solstation.com/stars/procyon2.htm Accessed 2/3/07.
- ^ Robert Burnham Jr., Burnham's Celestial Handbook (New York: Dover Publications Inc., 1978), p. 450.
- ^ Solstation.com
- ^ Provencal et al., "Procyon B: outside the iron box". Astrophys. J., 568, 324-334 (2002) - March(III) 2002 http://simbad3.u-strasbg.fr/cgi-bin/cdsbib4?2002ApJ...568..324P Accessed 2/3/07.
- ^ Holberg et al., "Sirius B: A New, More Accurate View". The Astrophysical Journal, 497: 935-942, 1998 April 20 http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v497n2/36707/36707.html?erFrom=5484718977321095316Guest Accessed 2/3/07.
- ^ Provencal et al.
