51 Pegasi

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51 Pegasi
Pegasus 51 location.png

The red circle shows the location of 51 Pegasi in Pegasus.
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Pegasus
Right ascension 22h 57m 27.98s [1]
Declination +20° 46′ 07.8″ [1]
Apparent magnitude (V) 5.49
Characteristics
Spectral type G2.5IVa or G4-5Va
Apparent magnitude (B) 6.16
Apparent magnitude (R) 5.12
Apparent magnitude (I) 4.80
Apparent magnitude (J) 4.66
Apparent magnitude (H) 4.23
Apparent magnitude (K) 3.91
U-B color index 0.22
B-V color index 0.67
V-R color index 0.37
R-I color index 0.32
Variable type Suspected
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 1.06 M☉
Radius 1.237 ± 0.047 [2] R☉
Surface gravity (log g) 3.89–4.21
Luminosity 1.30 L☉
Temperature 5571 ± 102 [2] K
Metallicity 160%
Rotation 37 days [3]
Age 7.5–8.5 Gyr
Other designations
GJ 882, HR 8729, BD +19°5036, HD 217014, LTT 16750, GCTP 5568.00, SAO 90896, HIP 113357.
Database references
SIMBAD data
NStED data
ARICNS data
Extrasolar Planets
Encyclopaedia		 data

51 Pegasi is a Sun-like star located 15.6 parsecs (50.9 light-years) from Earth[1] in the constellation Pegasus. It was the first Sun-like star, other than the Sun, found to have a planet orbiting it, a discovery that was announced in 1995.

The exoplanet's discovery was announced on October 6, 1995 by Michel Mayor and Didier Queloz.[4] The discovery was made with the radial velocity method at the Observatoire de Haute-Provence, using the ELODIE spectrograph.

The star itself is of apparent magnitude 5.49, and so is visible from the Earth with binoculars, or with the naked eye under dark sky conditions. 51 Pegasi is a yellow dwarf star estimated to be 7.5 billion years old, somewhat older than the Sun, 4–6% more massive, with more metal content and running low in hydrogen. Its spectral type is listed as either G2.5V or G4-5Va.

In 1996 astronomers Baliunas, Sokoloff, and Soon reported measurements of a sample of stars' Calcium II H and K spectral lines and thereby measured a rotational period of 37 days for 51 Pegasi.[3]

Contents

[edit] Planetary system

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

After the announcement, 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 for short) is the first discovered planetary-mass companion of its parent star. Further such companions would be designated c, d, and so on. 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.

The 51 Pegasi system[5]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity
b ≥ 0.472 ± 0.039 MJ 0.0527 ± 0.0030 4.230785 ± 0.000036 0.013 ± 0.012

[edit] See also

[edit] References

  1. ^ a b c d e f van Leeuwen, F. (2007). "HIP 113357". Hipparcos, the New Reduction. http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-out.add=.&-source=I/311/hip2&recno=112974. Retrieved 2009-12-09. 
  2. ^ a b Gerard T. van Belle and Kaspar von Braun (2009). "Directly Determined Linear Radii and Effective Temperatures of Exoplanet Host Stars" (abstract). The Astrophysical Journal 694 (2): 1085–1098. doi:10.1088/0004-637X/694/2/1085. http://www.iop.org/EJ/abstract/0004-637X/694/2/1085/. (web Preprint)
  3. ^ a b Baliunas et al. (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. doi:10.1086/309891. http://www.iop.org/EJ/article/1538-4357/457/2/L99/5296.html. .
  4. ^ Mayor, Michael; Queloz, Didier (1995). "A Jupiter-mass companion to a solar-type star". Nature 378 (6555): 355–359. doi:10.1038/378355a0. http://owww.phys.au.dk/~hans/exo/paper01.pdf. 
  5. ^ Butler et al. (2006). "Catalog of Nearby Exoplanets". The Astrophysical Journal 646 (1): 505–522. doi:10.1086/504701. http://www.iop.org/EJ/article/0004-637X/646/1/505/64046.html. 

[edit] External links

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

v • d • e
Stars of Pegasus
1 • 2 • 3 • 4 • 5 • 7 • ε (Enif) • 9 • κ • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • ν • 23 • ι • 25 • θ • π1 • 28 • π2 • 30 • 31 • 32 • 33 • 34 • 35 • 36 • 37 • 38 • 39 • 40 • 41 • ζ (Homam) • ο • η (Matar) • 45 • ξ • λ • μ (Sadalbari) • σ • ρ • 51 • 52 • β (Scheat) • α (Markab) • 55 • 56 • 57 • 58 • 59 • 60 • 61 • τ • 63 • 64 • 65 • 66 • 67 • υ • 69 • 70 • 71 • 72 • 73 • 74 • 75 • 76 • 77 • 78 • 79 • 80 • φ • 82 • 83 • ψ • 85 • 86 • 87 • γ • χ • 34 Vul
List

BD+19 5036

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