51 Pegasi
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 The red circle shows the location of 51 Pegasi in Pegasus. |
|
| Observation data Epoch J2000.0 |
|
|---|---|
| Constellation (pronunciation) |
Pegasus |
| Right ascension | 22h 57m 28.0s |
| Declination | +20° 46′ 08″ |
| Apparent magnitude (V) | 5.49 |
| Characteristics | |
| Spectral type | G2.5IVa or G4-5Va |
| 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: 208.07 mas/yr Dec.: 60.96 mas/yr |
| Parallax (π) | 65.10 ± 0.76 mas |
| Distance | 50.1 ly (15.4 pc) |
| Absolute magnitude (MV) | 4.51 |
| Details | |
| Mass | 1.06 M☉ |
| Radius | 1.15–1.4 R☉ |
| Surface gravity (log g) | 3.89–4.21 |
| Luminosity | 1.30 L☉ |
| Temperature | 5,665 K |
| Metallicity | 160% |
| Rotation | 37 days |
| Age | 7.5–8.5 × 109 years |
| Other designations | |
51 Pegasi is a Sun-like star (although somewhat older than the Sun) located 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 Michel Mayor and Didier Queloz.[1] 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 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.[2]
Contents |
[edit] Planetary system
The exoplanet's discovery was announced on October 6, 1995 by Michael Mayor and Didier Queloz.[1] They used 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 (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 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.
| Planet (in order from star) |
Mass (MJ) |
Orbital period (days) |
Semimajor axis (AU) |
Eccentricity |
|---|---|---|---|---|
| b | >0.468 ± 0.007 | 4.23077 ± 0.00005 | 0.052 | 0 |
[edit] See also
[edit] References
- ^ a b Mayor, Michel; Queloz, Didier (1995). "A Jupiter-mass companion to a solar-type star". Nature 378: 355 – 359. doi:.
- ^ Sallie Baliunas, Dmitry Sokoloff, and Willie Soon (1996 February 1). "Magnetic Field and Rotation in Lower Main-Sequence Stars: An Empirical Time-Dependent Magnetic Bode's Relation?". THE ASTROPHYSICAL JOURNAL 457 (Number 2, Part 2): L99–L102..
