Gamma Cephei Ab

Gamma Cephei Ab (abbreviated γ Cephei Ab, γ Cep Ab), formally named Tadmor /ˈtædmɔːr/, is an exoplanet approximately 45 light-years away in the constellation of Cepheus (the King). The planet was confirmed to be in orbit around Gamma Cephei A in 2002, but was first suspected to exist around 1988 (making this planet arguably the first true exoplanet discovered).

γ Cephei Ab / Tadmor
Discovery
Discovered byBruce Campbell, Gordon Walker, Stephenson Yang,[1] Hatzes et al.
Discovery siteUnited States
Discovery date13 July 1988 (suspected)
24 September 2002 (confirmed)
Doppler spectroscopy
Orbital characteristics
2.05±0.06 AU
Eccentricity0.049±0.034[2]
903.3±1.5[2] d
2,453,227±87[2]
94.6±34.6[2]
Semi-amplitude27.5 ± 1.5
Starγ Cephei A
Physical characteristics
Mass9.4+0.7
−1.1 MJ[3]

    Naming

    In July 2014 the International Astronomical Union (IAU) launched NameExoWorlds, a process for giving proper names to certain exoplanets.[4] The process involved public nomination and voting for the new names.[5] In December 2015, the IAU announced the winning name for this planet was Tadmor.[6] It was submitted by the Syrian Astronomical Association and is the ancient Semitic name and modern Arabic name for the city of Palmyra, a (UNESCO) World Heritage Site.[7]

    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,[8] 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 However, the claim was retracted in 1992 due to the quality of the data not being good enough to make a solid discovery.[9]

    2002 confirmation

    On 24 September 2002, 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 MJ (1.59 times that of Jupiter).[10] The parameters were later recalculated when direct detection of the secondary star γ Cephei B allowed astronomers to better constrain the properties of the system.[11] 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.

    Astrometric observations

    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 brown or red dwarf.[12]

    In 2018, Hubble astrometric observations revealed the true mass of γ Cephei Ab to be 9.4 MJ.[3]

    See also

    References
    1. "ESA Science & Technology - A brief introduction to exoplanets". sci.esa.int. Retrieved 2023-02-04.
    2. Endl, Michael; et al. (2011). News from the γ Cephei Planetary System. PLANETARY SYSTEMS BEYOND THE MAIN SEQUENCE: Proceedings of the International Conference. AIP Conference Proceedings. Vol. 1331. pp. 88–94. arXiv:1101.2588. Bibcode:2011AIPC.1331...88E. doi:10.1063/1.3556187.
    3. Benedict, G. Fritz; Harrison, Thomas E.; Endl, M.; Torres, G. (April 2018). "A Mass for γ Cep Ab". Research Notes of the AAS. 2 (2): 7. Bibcode:2018RNAAS...2....7B. doi:10.3847/2515-5172/aabe7e. S2CID 188154737. Retrieved 29 July 2022.
    4. NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars. IAU.org. 9 July 2014
    5. "NameExoWorlds The Process". Archived from the original on 2015-08-15. Retrieved 2015-09-05.
    6. Final Results of NameExoWorlds Public Vote Released, International Astronomical Union, 15 December 2015.
    7. "NameExoWorlds The Approved Names". Archived from the original on 2018-02-01. Retrieved 2015-12-30.
    8. "ESA Science & Technology - A brief introduction to exoplanets". sci.esa.int. Retrieved 2023-02-04.
    9. Boss, Alan (2009). The Crowded Universe: The Search for Living Planets. Basic Books. ISBN 978-0-465-00936-7.
    10. Hatzes, Artie P.; et al. (2003). "A Planetary Companion to Gamma Cephei A". The Astrophysical Journal. 599 (2): 1383–1394. arXiv:astro-ph/0305110. Bibcode:2003ApJ...599.1383H. doi:10.1086/379281. S2CID 11506537.
    11. Neuhäuser, R.; et al. (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. arXiv:astro-ph/0611427. Bibcode:2007A&A...462..777N. doi:10.1051/0004-6361:20066581. S2CID 17530531.
    12. Torres, Guillermo (2007). "The Planet Host Star γ Cephei: Physical Properties, the Binary Orbit, and the Mass of the Substellar Companion". The Astrophysical Journal. 654 (2): 1095–1109. arXiv:astro-ph/0609638. Bibcode:2007ApJ...654.1095T. doi:10.1086/509715. S2CID 13255217.
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