Epsilon Tauri b

Epsilon Tauri b / Amateru
Artistic simulation of Epsilon Tauri b orbiting its host star.
Discovery[1]
Discovered bySato et al.
Discovery date7 February 2007
Doppler spectroscopy
Orbital characteristics[2]
Semi-major axis
1.878±0.001 AU
Eccentricity0.076+0.009
−0.008
585.82+0.26
−0.33 d
2453492.3+11.3
−10.0 JD
Argument of periastron
107.90°+6.82°
−6.07°
Semi-amplitude93.24+0.74
−0.73 m/s
StarEpsilon Tauri
Physical characteristics[2]
Mass≥7.190±0.056 MJ

    Epsilon Tauri b (abbreviated ε Tauri b or ε Tau b), formally named Amateru /æməˈtɛruː/, is a super-Jupiter exoplanet orbiting the K-type giant star Epsilon Tauri approximately 146 light-years (45 parsecs) away from the Earth in the constellation of Taurus.[3] It orbits the star further out than Earth orbits the Sun. It has moderate eccentricity.[1]

    The planet orbits one of the four giant stars in the Hyades star cluster, and was the first planet ever discovered in an open cluster.[1]

    Name

    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 was Amateru for this planet.[6] The name was based on that submitted by the Kamagari Astronomical Observatory of Kure, Hiroshima Prefecture, Japan: namely 'Amaterasu', the Shinto goddess of the Sun, born from the left eye of the god Izanagi. The IAU substituted 'Amateru' - which is a common Japanese appellation for shrines when they enshrine Amaterasu - because 'Amaterasu' is already used for asteroid 10385 Amaterasu.[7]

    Characteristics

    Mass, radius and temperature

    Epsilon Tauri b is a "super-Jupiter", an exoplanet that has a mass larger than that of the gas giants Jupiter and Saturn. It has a temperature of 541 K (268 °C; 514 °F). It has a minimum mass of around 7.2 MJ[2] and a potential radius of around 18% larger than Jupiter (1.18 RJ, or 12 R🜨) based on its mass, since it is more massive than the jovian planet.

    Host star

    The planet orbits a (K-type) giant star named Epsilon Tauri. It has exhausted the hydrogen supply in its core and is currently fusing helium. The star has a mass of 2.7 M☉ and a radius of around 12.6 R☉. It has a surface temperature of 4901 K and is 625 million years old. In comparison, the Sun is about 4.6 billion years old[8] and has a surface temperature of 5778 K.[9]

    The star's apparent magnitude, or how bright it appears from Earth's perspective, is 3.53. Therefore, Epsilon Tauri can be seen with the naked eye.

    Orbit

    Epsilon Tauri b orbits its star with about 78 times the Sun's luminosity (78 L☉) every 586 days at a distance of 1.88 AU (compared to Mars' orbital distance from the Sun, which is 1.52 AU). It has a mildly eccentric orbit, with an eccentricity of 0.08.[2]

    Discovery

    Epsilon Tauri b was discovered by using the High Dispersion Echelle Spectrograph at Okayama Astrophysical Observatory (OAO) as part of a process to study G-type and K-type giant stars to search for exoplanets. Measurements of radial velocity from Epsilon Tauri were taken between December 2003 and July 2006.[1] Wobbles in the star were detected, and after analyzing the data, it was eventually concluded that there was a planetary companion with a mass 7 times that of Jupiter orbiting Epsilon Tauri every 595 days, or nearly 2 years with an eccentricity of 0.15.[1] These values were later refined to a period of 586 days and an eccentricity of 0.08.[2]

    The planet Amateru is mentioned by name in the science fiction book Starsong Chronicles: Exodus by American author JJ Clayborn.[10]

    See also

    References

    1. 1 2 3 4 5 Sato, Bun'ei; et al. (2007). "A Planetary Companion to the Hyades Giant ε Tauri". The Astrophysical Journal. 661 (1): 527–531. Bibcode:2007ApJ...661..527S. doi:10.1086/513503.
    2. 1 2 3 4 5 Teng, Huan-Yu; Sato, Bun'ei; et al. (August 2023). "Revisiting planetary systems in the Okayama Planet Search Program: A new long-period planet, RV astrometry joint analysis, and a multiplicity-metallicity trend around evolved stars". Publications of the Astronomical Society of Japan. 75 (6): 1030–1071. arXiv:2308.05343. Bibcode:2023PASJ...75.1030T. doi:10.1093/pasj/psad056.
    3. ↑ "Epsilon Tauri b". NASA Exoplanet Archive. Retrieved 28 July 2016.
    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 2015-12-21.
    8. ↑ Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 19 February 2011.
    9. ↑ Fraser Cain (September 15, 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011.
    10. ↑ Clayborn, JJ (March 2017), Starsong Chronicles: Exodus, Independently Published, ISBN 978-1520611747
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