Gamma Cephei Ab (abbreviated γ Cephei Ab, γ Cep Ab), formally named Tadmor , is an

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...

approximately 45 light-years away in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

of Cepheus that orbits Gamma Cephei A. The planet was suspected to exist in 1988, and later confirmed in 2003, technically making it the first exoplanet discovered.

Naming

In July 2014 the International Astronomical Union (IAU) launched NameExoWorlds, a process for giving proper names to certain exoplanets. The process involved public nomination and voting for the new names. In December 2015, the IAU announced the winning name for this planet was Tadmor. It was submitted by the

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n Astronomical Association and is the ancient Semitic name and modern

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name for the city of Palmyra, a (

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) World Heritage Site.

Detection and discovery

1988 claims

The first indications of γ Cephei Ab were reported in July 1988. The planet was tentatively identified by a Canadian team of astronomers, which was led 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 would have been the first ''true'' discovery of an 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 However, the claim was retracted in 1992 due to the quality of the data not being good enough to make a solid discovery.

2003 confirmation

On 7 May 2003, γ Cephei Ab was finally confirmed. The team of astronomers (including William D. Cochran, Artie P. Hatzes, et al.) at the Planetary Systems and their Formation Workshop announced the preliminary confirmation of a long-suspected planet γ Cephei Ab with a minimum mass of 1.59 M_J (1.59 times that of

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...

). The parameters were later recalculated when direct detection of the secondary

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

γ Cephei B allowed astronomers to better constrain the properties of the system. γ 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 AU in orbital distance around γ Cephei A, which would place it from slightly beyond the orbit of Mars to the inner asteroid belt in the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

Astrometric observations

'' Hipparcos'' data taken in 2006 constrains its mass below "13.3 M_J at the 95% confidence level, and 16.9 M_J 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 brown or red dwarf. In 2018, Hubble astrometric observations revealed the true mass of γ Cephei Ab to be 9.4 .

References

External links

* * {{DEFAULTSORT:Gamma Cephei Ab Gamma Cephei Exoplanets discovered in 1988 Giant planets Exoplanets with proper names Exoplanets detected by radial velocity Exoplanets detected by astrometry