51 Pegasi is a Sun-like star 15.4 parsecs (50.1 light-years) from Earth in the constellation Pegasus. It was the first Sun-like star to be 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 Michael Mayor and Didier Queloz in Nature, volume 378, page 355. The discovery was made with the radial velocity method at the Observatoire de Haute-Provence.

The star itself is of apparent magnitude 5.49, and so is visible from the Earth with binoculars, or with the naked eye by those with good vision in very 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.

Planetary system

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The exoplanet's discovery was announced on October 6 1995 by Michael Mayor and Didier Queloz in Nature, volume 378, page 355, using the radial velocity method at the Observatoire de Haute-Provence with the ELODIE spectrograph.

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 or 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 1000 Celsius, 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.

In 2006, the possibility of 51 Pegasi c became likely, but doubtful. ^*

See also

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• PSR 1257+12
• Solar twin
• 55 Cancri
• 70 Virginis
• 47 Ursae Majoris
• Tau Boötis

References

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2. (lists rotational periods for 112 stars)

External links

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• 51 Pegasus at SolStation.com.
• ARICNS
• nStars database entry
• David Darling's encyclopedia

Flamsteed objects | HD and HDE objects | HIP objects | Pegasus constellation | Yellow dwarfs

51 Pegasi | Pegasus 51 | 51 Pegasi | 51 Pegasi | 51 Pegasi | 51 Pegasi | ペガスス座51番星 | 51 Pegasi | 51 Пегаса | 51 Pegasi | 51 Pegasi | 飛馬座51