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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

Planetary system

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

See also

References

External links

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

BD+19 5036

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Simple English

File:Pegasus 51
The red circle shows where 51 Pegasi is inside the constellation Pegasus.

51 Pegasi is a star that is like our Sun and can be found 15.4 parsecs (50.1 light-years) away from the Earth in the constellation Pegasus. It was the first Sun-like star, other than the Sun, found to have a planet orbiting it, this discovery was first made public in 1995.[1]

The exoplanet's discovery was made public on October 6, 1995 by Michel Mayor and Didier Queloz.[2] The discovery was made using the radial velocity method at the Observatoire de Haute-Provence, using a tool called the ELODIE spectrograph that is used to find planets that are outside our Solar System.

The star itself has an apparent brightness of 5.49, and because of this it is able to be seen from the Earth with binoculars, or with the naked eye if it is dark outside. 51 Pegasi is a yellow dwarf star that is thought to be around 7.5 billion years old, which is somewhat older than our Sun. 51 Pegasi is also 4-6% more massive than our Sun with more metal content. However, it is running low on hydrogen.

In 1996 astronomers Baliunas, Sokoloff, and Soon calculated that it takes 51 Pegasi b 37 days to orbit 51 Pegasi.[3]

Planetary system

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After the announcement, on October 12, 1995, more proof that this star did exist came from Dr. Geoffrey Marcy from San Francisco State University and Dr. R. Paul Butler from the University of California, Berkeley using the Hamilton Spectrograph at the Lick Observatory near San Jose in California.

51 Pegasi b is the first discovered planet of its parent star, 51 Pegasi. If any more are discovered they will be named 51 Pegasi c, 51 Pegasi d, and so on. The planet has been informally named Bellerophon. After its discovery, many teams proved its existence and continued to find out more about its properties, including the fact that it orbits very close to the star, has estimated temperatures around 1200 Celsius, and has a minimum mass about half that of Jupiter.

References

  1. NASA
  2. Mayor, Michael; Queloz, Didier (1995). [Expression error: Unexpected < operator "A Jupiter-mass companion to a solar-type star"]. Nature 378 (6555): 355–359. doi:10.1038/378355a0. 
  3. Sallie Baliunas, Dmitry Sokoloff, and Willie Soon (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.journals.uchicago.edu/doi/full/10.1086/309891. .

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