51 Pegasi

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51 Pegasi
Pegasus constellation map.svg
Locator Dot2.gif

The red dot shows the location of 51 Pegasi in Pegasus.
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Pegasus
Right ascension 22h 57m 27.98004s[1]
Declination +20° 46′ 07.7912″[1]
Apparent magnitude (V) 5.49[2]
Characteristics
Spectral type G5V[3]
Apparent magnitude (B) 6.16[4]
Apparent magnitude (R) 5.0[4]
Apparent magnitude (I) 4.7[4]
Apparent magnitude (J) 4.66[4]
Apparent magnitude (H) 4.23[4]
Apparent magnitude (K) 3.91[2]
U−B color index +0.20[5]
B−V color index +0.67[5]
V−R color index 0.37
R−I color index 0.32
Astrometry
Radial velocity (Rv) -33.7 km/s
Proper motion (μ) RA: 207.25 ± 0.31[1] mas/yr
Dec.: 60.34 ± 0.30[1] mas/yr
Parallax (π) 64.07 ± 0.38[1] mas
Distance 50.9 ± 0.3 ly
(15.61 ± 0.09 pc)
Absolute magnitude (MV) 4.51
Details
Mass 1.11[3] M
Radius 1.237 ± 0.047[2] R
Luminosity 1.30 L
Surface gravity (log g) 4.33[6] cgs
Temperature 5571 ± 102[2] K
Metallicity [Fe/H] 0.20[6] dex
Rotation 21.9 ± 0.4 days[7]
Age 6.1–8.1[8] Gyr
Other designations
51 Peg, GJ 882, HR 8729, BD +19°5036, HD 217014, LTT 16750, GCTP 5568.00, SAO 90896, HIP 113357.[9]
Database references
SIMBAD data
Exoplanet Archive data
ARICNS data
Extrasolar Planets
Encyclopaedia
data

51 Pegasi (abbreviated 51 Peg) is a Sun-like star located 50.9 light-years (15.6 parsecs)[1] from Earth in the constellation Pegasus. It was the first extrasolar Sun-like star found to have a planet orbiting it.[10]

Properties[edit]

51 Pegasi

The star is of apparent magnitude 5.49, and so is visible with the naked eye under suitable viewing conditions. The Flamsteed designation for this star, 51 Pegasi, was assigned by John Flamsteed in his star atlas published in 1712.

51 Pegasi has a stellar classification of G5V,[3] indicating that it is a main sequence star that is generating energy through the thermonuclear fusion of hydrogen at its core. The effective temperature of the chromosphere is about 5571 K, giving 51 Pegasi the characteristic yellow hue of a G-type star.[11] It is estimated to be 6.1–8.1 billion years old, somewhat older than the Sun, with a radius 24% larger and 11% more massive. The star has a higher proportion of elements other than hydrogen/helium compared to the Sun; a quantity astronomers term a star's metallicity. Stars with higher metallicity such as this are more likely to host planets.[3] In 1996 astronomers Baliunas, Sokoloff, and Soon measured a rotational period of 37 days for 51 Pegasi.[12]

Although the star was suspected of being variable during a 1981 study,[13] subsequent observation showed there was almost no chromospheric activity between 1977 and 1989. Further examination between 1994 and 2007 showed a similar low or flat level of activity. This, along with its relatively low X-ray emission, suggests that the star may be in a Maunder minimum period[3] during which a star produces a reduced number of star spots.

The star rotates at an inclination of 79+11
−30
degrees relative to Earth.[7]

Planetary system[edit]

Artist's conception of 51 Pegasi and orbiting planet 51 Pegasi b.

On October 6, 1995, Swiss astronomers Michel Mayor and Didier Queloz announced the discovery of an exoplanet orbiting 51 Pegasi.[10] The discovery was made with the radial velocity method on a telescope at Observatoire de Haute-Provence in France and using the ELODIE spectrograph. On October 12, 1995, confirmation came from Dr. Geoffrey Marcy from San Francisco State University and Dr. Paul Butler from the University of California, Berkeley using the Hamilton Spectrograph at the Lick Observatory near San Jose in California.

51 Pegasi b (51 Peg b) is the first discovered planetary-mass companion of its parent star. The planet has been informally named Bellerophon. After its discovery, many teams confirmed its existence and obtained more observations of its properties, including the fact that it orbits very close to the star, suffers estimated temperatures around 1200°C, and has a minimum mass about half that of Jupiter. At the time, this close distance was not compatible with theories of planet formation and resulted in discussions of planetary migration. It has been assumed that the planet shares the star's inclination of 79 degrees.[14] However, several "hot Jupiters" are now known to be oblique relative to the stellar axis.[15] As of 2012, no additional planets have been found orbiting this star.

The 51 Pegasi system[16]
Companion
(in order from star)
Mass Semimajor axis
(AU)
Orbital period
(days)
Eccentricity Inclination Radius
b ≥ 0.472 ± 0.039 MJ 0.0527 ± 0.0030 4.230785 ± 0.000036 0.013 ± 0.012

See also[edit]

References[edit]

  1. ^ a b c d e f van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d van Belle, Gerard T.; von Braun, Kaspar (2009). "Directly Determined Linear Radii and Effective Temperatures of Exoplanet Host Stars". The Astrophysical Journal (abstract) 694 (2): 1085–1098. arXiv:0901.1206. Bibcode:2009ApJ...694.1085V. doi:10.1088/0004-637X/694/2/1085. 
  3. ^ a b c d e Poppenhäger, K. et al. (December 2009), "51 Pegasi - a planet-bearing Maunder minimum candidate", Astronomy and Astrophysics 508 (3): 1417–1421, arXiv:0911.4862, Bibcode:2009A&A...508.1417P, doi:10.1051/0004-6361/200912945 
  4. ^ a b c d e Monet, David G. et al. (February 2003). "The USNO-B Catalog". The Astronomical Journal 125 (2): 984–993. arXiv:astro-ph/0210694. Bibcode:2003AJ....125..984M. doi:10.1086/345888. 
  5. ^ a b Johnson, H. L. et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory 4 (99). Bibcode:1966CoLPL...4...99J. 
  6. ^ a b Frasca, A. et al. (December 2009). "REM near-IR and optical photometric monitoring of pre-main sequence stars in Orion. Rotation periods and starspot parameters". Astronomy and Astrophysics 508 (3): 1313–1330. Bibcode:2009A&A...508.1313F. doi:10.1051/0004-6361/200913327. 
  7. ^ a b Simpson, E. K. et al. (November 2010), "Rotation periods of exoplanet host stars", Monthly Notices of the Royal Astronomical Society 408 (3): 1666–1679, arXiv:1006.4121, Bibcode:2010MNRAS.408.1666S, doi:10.1111/j.1365-2966.2010.17230.x  [as "HD 217014"]
  8. ^ Mamajek, Eric E.; Hillenbrand, Lynne A. (November 2008). "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics". The Astrophysical Journal 687 (2): 1264–1293. arXiv:0807.1686. Bibcode:2008ApJ...687.1264M. doi:10.1086/591785. 
  9. ^ "51 Peg – Star suspected of Variability". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2011-12-17. 
  10. ^ a b Mayor, Michael; Queloz, Didier (1995). "A Jupiter-mass companion to a solar-type star". Nature 378 (6555): 355–359. Bibcode:1995Natur.378..355M. doi:10.1038/378355a0. 
  11. ^ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, retrieved 2012-01-16 
  12. ^ Baliunas, Sallie; Sokoloff, Dmitry; Soon, Willie (1996). "Magnetic Field and Rotation in Lower Main-Sequence Stars: An Empirical Time-Dependent Magnetic Bode's Relation?". The Astrophysical Journal Letters 457 (2): L99–L102. Bibcode:1996ApJ...457L..99B. doi:10.1086/309891. .
  13. ^ Kukarkin, B. V. et al. (1981). Nachrichtenblatt der Vereinigung der Sternfreunde e.V. (Catalogue of suspected variable stars). Moscow: Academy of Sciences USSR Shternberg. Bibcode:1981NVS...C......0K. 
  14. ^ "51_peg_b". Extrasolar Planet Encyclopaedia. Retrieved November 12, 2012. 
  15. ^ Roberto Sanchis-Ojeda, Josh N. Winn, Daniel C. Fabrycky (2012). Starspots and spin-orbit alignment for Kepler cool host stars. arXiv:1211.2002. Bibcode:2013AN....334..180S. doi:10.1002/asna.201211765. 
  16. ^ Butler, R. P. et al. (2006). "Catalog of Nearby Exoplanets". The Astrophysical Journal 646 (1): 505–522. arXiv:astro-ph/0607493. Bibcode:2006ApJ...646..505B. doi:10.1086/504701. 

External links[edit]

Coordinates: Sky map 22h 57m 28.0s, +20° 46′ 08″