Gamma Cephei Ab

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**Gamma Cephei Ab**
Parent star
Extrasolar planet		List of extrasolar planets
Star		Gamma Cephei A
Constellation		Cepheus
Right ascension	(α)	23^h 39^m 20.8^s
Declination	(δ)	+77° 37′ 56″
Distance		45 ± 0.3 ly (13.81 ± 0.1 pc)
Spectral type		K1IVe
Orbital elements
Semimajor axis	(a)	2.044 AU
Eccentricity	(e)	0.115 ± 0.069
Orbital period	(P)	902.96 ± 6 d (2.47 y)
Angular distance	(θ)	173.22 mas
Longitude of periastron	(ω)	75.6 ± 18.8°
Time of periastron	(T₀)	2,453,156.8 ± 52.4 JD
Semi-amplitude	(K)	27.5 ± 1.5 m/s
Physical characteristics
Mass	(m)	>1.59 M_J
Discovery information
Discovery date		July 13, 1988 and confirmed on Sept 24, 2002
Discoverer(s)		Campbell, Walker, Yang et al.
Detection method		Doppler Spectroscopy
Discovery status		Confirmed

Gamma Cephei Ab is an extrasolar planet orbiting Gamma Cephei A every two years.

1 Discovery
2 Orbit and mass
3 See also
4 References
5 External links

[edit] Discovery

A planet orbiting Gamma Cephei A was tentatively identified by a Canadian team of Bruce Campbell, Gordon Walker, and Stephenson Yang in July 1988. Its existence was also announced by Anthony Lawton and P. Wright in 1989. This would have been the first confirmed 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 However, the claim was retracted in 1992 due to the quality of the data not being good enough to make a solid discovery. But 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 times that of Jupiter.

[edit] Orbit and mass

Gamma Cephei moves between 1.81 and 2.28 AUs in orbital distance around Gamma Cephei A, with an average separation of around 2.044 AUs, which would be placed beyond the orbit of Mars in the solar system. Its orbit has an eccentricity of 0.115 and takes 2.47 years to complete.