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| Extrasolar planet | List of extrasolar planets | |
|---|---|---|
| Parent star | ||
| Star | Gamma Cephei A | |
| Constellation | Cepheus | |
| Right ascension | (α) | 23h 39m 20.8s |
| Declination | (δ) | +77° 37′ 56″ |
| Distance | 44.9 ± 0.31 ly (13.76 ± 0.081 pc) |
|
| Spectral type | K1IVe | |
| Orbital elements | ||
| Semimajor axis | (a) | 2.044 ± 0.0571 AU |
| Eccentricity | (e) | 0.115 ± 0.0581 |
| Orbital period | (P) | 902.9 ± 3.51 d (2.472 ± 0.0101 y) |
| Argument of periastron |
(ω) | 63 ± 271° |
| Time of periastron | (T0) | 2,453,156.8 ± 52.4 JD |
| Semi-amplitude | (K) | 27.5 ± 1.5 m/s |
| Physical characteristics | ||
| Mass | (m) | >1.60 ± 0.131 MJ |
| Discovery information | ||
| Discovery date | 13 July 1988 (suspected) 24 September 2002 |
|
| Discoverer(s) | Hatzes et al. | |
| Detection method | Doppler spectroscopy | |
| Discovery site |  United States |
|
| Discovery status | Confirmed | |
Gamma Cephei Ab is an extrasolar planet approximately 45 light-year away in the constellation of Cepheus (the King). The planet was confirmed to orbit Gamma Cephei in 2002, but was suspected to be a planet around 1988 (making this planet the first true extrasolar planet discovered).
Contents |
Detection and discovery
1988 claims
The first indications of Gamma Cephei Ab were reported in July 1988. The planet was tentatively identified by a Canadian team of astronomers (lead by Bruce Campbell, Gordon Walker, and Stephenson Yang, while its existence was also announced by Anthony Lawton and P. Wright in 1989. Though not confirmed, this world would have been the first true extrasolar planet, and it was hypothesized based on the same radial velocity technique later used successfully by others. However, the claim was retracted in 1992 due to the quality of the data not being good enough to make a solid discovery.
2002 confirmation
On September 24, 2002, Gamma Cephei Ab was finally confirmed. The team of astronomers (including William D. Cochran, Artie P. Hatzes... etc.) at the Planetary Systems and their Formation Workshop announced the preliminary confirmation of a long-suspected planet Gamma Cephei Ab with a minimum mass of 1.59 MJ (1.59 times that of Jupiter).2 The parameters were later recalculated when direct detection of the secondary star Gamma Cephei B allowed astronomers to better constrain the properties of the system.1 Gamma Cephei Ab moves in an elliptical orbit with a semimajor axis of 2.044 AU which takes almost two and a half years to complete. The eccentricity is 0.115, which means it moves between 1.81 and 2.28 AUs in orbital distance around Gamma Cephei A, which would place it beyond the orbit of Mars in the solar system.
Hipparcos data taken in 2006 constrains its mass below "13.3 MJ at the 95% confidence level, and 16.9 MJ at the 99.73% (3 σ) confidence level". This is not much to go on, but it is enough to verify that it is not another unseen red or brown dwarf.3
See also
References
- ^ a b c d e f g h i Neuhäuser, R.; Mugrauer, M.; Fukagawa, M.; Torres, G.; Schmidt, T. (2007). "Direct detection of exoplanet host star companion γ Cep B and revised masses for both stars and the sub-stellar object". Astronomy and Astrophysics 462 (2): 777–780. doi:. http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?2007A%26A...462..777N&db_key=AST&nosetcookie=1.
- ^ Hatzes et al. (2003). "A Planetary Companion to Gamma Cephei A". The Astrophysical Journal 599 (2): 1383 – 1394. doi:. http://www.journals.uchicago.edu/doi/full/10.1086/379281.
- ^ Guillermo Torres (2007). "The Planet Host Star γ Cephei: Physical Properties, the Binary Orbit, and the Mass of the Substellar Companion" (abstract). The Astrophysical Journal 654 (2): 1095–1109. doi:. http://www.journals.uchicago.edu/doi/abs/10.1086/509715.
External links
- "A Planetary Companion to the Binary Star Gamma Cephei". McDonald Observatory. Retrieved on 2008-06-23.
- "Errai 2". SolStation. Retrieved on 2008-06-23.
- "Gamma Cephei Ab". Extrasolar Visions. Retrieved on 2008-06-23.
- "Notes for planet Gamma Cephei b". The Extrasolar Planets Encyclopaedia. Retrieved on 2008-06-23.
