Procyon

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This article is about the star. Procyon is also the mammalian genus to which raccoons belong.
Procyon A/B

The position of Procyon.
Observation data
Epoch J2000
Constellation
(pronunciation)		 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☉
Surface gravity (log g) 4.0/8.0[1]
Luminosity 7.73/0.00055 L☉
Temperature 6,650/9,700 K
Metallicity 110% Sun
Age 1.7 × 109 years
Visual binary orbit
Companion Procyon B
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
Database references
SIMBAD data

Procyon (IPA: 'pɹaʊ ˌsɪi ɒn) (α CMi / α Canis Minoris / Alpha Canis Minoris) is the brightest star in the constellation Canis Minor and the seventh brightest star in the nighttime sky with a visual apparent magnitude of 0.34. What appears as a single star to the naked eye 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.

Contents

[edit] 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.

An illustration of Procyon B's orbit, with Procyon A treated as fixed. This is how the orbit would appear from above, not as it actually appears from Earth.
An illustration of Procyon B's orbit, with Procyon A treated as fixed. This is how the orbit would appear from above, not as it actually appears from Earth.

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.[5] 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.[6]

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.[7],[8] 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.

[edit] Oscillations controversy

In late June of 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.[9] However others argued that the non-detection was consistent with published ground-based radial velocity observations of solar-like oscillations.[10][11]

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

[edit] Etymology and cultural significance

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.

[edit] References

  1. ^ Provencal, J. L.; Shipman, H. L.; Koester, Detlev; Wesemael, F.; Bergeron, P. (2002). "Procyon B: Outside the Iron Box". The Astrophysical Journal 568 (1): 324-334. doi:10.1086/338769. 
  2. ^ 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.
  3. ^ 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.
  4. ^ Solstation.com, "Procyon 2". http://www.solstation.com/stars/procyon2.htm Accessed 2/3/07.
  5. ^ Robert Burnham Jr., Burnham's Celestial Handbook (New York: Dover Publications Inc., 1978), p. 450.
  6. ^ Solstation.com
  7. ^ 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.
  8. ^ 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.
  9. ^ Matthews, J. M. et al: "No stellar p-mode oscillations in space-based photometry of Procyon" Nature 430:921 (2004) http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2004Natur.430...51M&db_key=AST&data_type=HTML&format=&high=44cedd215812216
  10. ^ Bouchy, F. et al.: "Oscillations on the star Procyon" Nature 432:7015 (2004) http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2005astro.ph.10303B&db_key=PRE&data_type=HTML&format=&high=44cedd215813511
  11. ^ Bedding, T. R. et al.: "The non-detection of oscillations in Procyon by MOST: Is it really a surprise?" Astronomy and Astrophysics, 432:L43 (2005) http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2005A%26A...432L..43B&db_key=AST
  12. ^ Bruntt, H. et al.: "Evidence for Granulation and Oscillations in Procyon from Photometry with the WIRE Satellite" The Astrophysical Journal, 633:440 (2005) http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2005ApJ...633..440B&db_key=AST&nosetcookie=1

[edit] See also

[edit] External links