Astronomy:Gamma Cephei Ab
| Discovery | |
|---|---|
| Discovered by | Bruce Campbell, Gordon Walker, Stephenson Yang,[1] Hatzes et al. |
| Discovery site | United States |
| Discovery date | 13 July 1988 (suspected) 24 September 2002 (confirmed) |
| Doppler spectroscopy | |
| Orbital characteristics | |
| 2.05±0.06 AU | |
| Eccentricity | 0.049±0.034[2] |
| Orbital period | 903.3±1.5[2] d |
| astron|astron|helion}} | 2,453,227±87[2] |
| 94.6±34.6[2] | |
| Semi-amplitude | 27.5 ± 1.5 |
| Star | γ Cephei A |
| Physical characteristics | |
| Mass | 9.4+0.7 −1.1 Jupiter mass[3] |
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).
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 Canada 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 However, the claim was retracted in 1992 due to the quality of the data not being good enough to make a solid discovery.[9]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 |♃|J}}}}}}.[3]
See also
References
- ↑ "ESA Science & Technology - A brief introduction to exoplanets" (in en-US). https://sci.esa.int/web/exoplanets/-/60654-a-brief-introduction-to-exoplanets.
- ↑ 2.0 2.1 2.2 2.3 Endl, Michael; Cochran, William D.; Hatzes, Artie P.; Wittenmyer, Robert A. (2011). "News from the γ Cephei Planetary System". PLANETARY SYSTEMS BEYOND THE MAIN SEQUENCE: Proceedings of the International Conference.. 1331. pp. 88–94. doi:10.1063/1.3556187. Bibcode: 2011AIPC.1331...88E.
- ↑ 3.0 3.1 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. doi:10.3847/2515-5172/aabe7e. Bibcode: 2018RNAAS...2....7B.
- ↑ NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars. IAU.org. 9 July 2014
- ↑ "NameExoWorlds The Process". http://nameexoworlds.iau.org/process.
- ↑ Final Results of NameExoWorlds Public Vote Released, International Astronomical Union, 15 December 2015.
- ↑ "NameExoWorlds The Approved Names". http://nameexoworlds.iau.org/names.
- ↑ "ESA Science & Technology - A brief introduction to exoplanets" (in en-US). https://sci.esa.int/web/exoplanets/-/60654-a-brief-introduction-to-exoplanets.
- ↑ Boss, Alan (2009). The Crowded Universe: The Search for Living Planets. Basic Books. ISBN 978-0-465-00936-7.
- ↑ Hatzes, Artie P. et al. (2003). "A Planetary Companion to Gamma Cephei A". The Astrophysical Journal 599 (2): 1383–1394. doi:10.1086/379281. Bibcode: 2003ApJ...599.1383H.
- ↑ 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. doi:10.1051/0004-6361:20066581. Bibcode: 2007A&A...462..777N.
- ↑ 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. doi:10.1086/509715. Bibcode: 2007ApJ...654.1095T.
External links
- "A Planetary Companion to the Binary Star Gamma Cephei". McDonald Observatory. http://austral.as.utexas.edu/planets/gamcep/gamcep.html.
- "Errai 2". SolStation. http://www.solstation.com/stars2/errai2.htm.
Coordinates: 
23h 39m 20.8s, +77° 37′ 56″
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