Epsilon Tauri b / Amateru
Discovery
Discovered bySato et al.
Discovery date7 February 2007
Doppler spectroscopy
Orbital characteristics
1.93 (± 0.03) AU
Eccentricity0.151 (± 0.023)
645.5 (± 5.3) d
2,452,879 ± 12
94.4 ± 7.4
Semi-amplitude98.5 ± 1.8
StarEpsilon Tauri
Physical characteristics
Mean radius
~1.18 RJ
Mass7.6 (± 0.2) MJ
Temperature541 K (268 °C; 514 °F)

    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 155 light-years (47.53 parsecs, or nearly 1.466×1015 km) away from the Earth in the constellation of Taurus.[1] It orbits the star further out than Earth orbits the Sun. It has moderate eccentricity.[2]

    Name

    In July 2014, the International Astronomical Union (IAU) launched NameExoWorlds, a process for giving proper names to certain exoplanets.[3] The process involved public nomination and voting for the new names.[4] In December 2015, the IAU announced the winning name was Amateru for this planet.[5] 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.[6]

    Characteristics

    Mass, radius and temperature

    Epsilon Tauri b is a "super-Jupiter", an exoplanet that has a radius and mass larger than that of the gas giants Jupiter and Saturn. It has a temperature of 541 K (268 °C; 514 °F). It has an estimated mass of around 7.6 MJ 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[7] and has a surface temperature of 5778 K.[8]

    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 nearly 97 times the Sun's luminosity (97 L☉) every 645 days at a distance of 1.93 AU (compared to Mars' orbital distance from the Sun, which is 1.52 AU). It has a mildly eccentric orbit, with an eccentricity of 0.15.

    Discovery

    Epsilon Tauri b was discovered by using the High Dispersion Echelon 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.[2] 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 645 days, or nearly 2 years with an eccentricity of 0.15.

    See also

    The planet Amateru is mentioned by name in the science fiction book Starsong Chronicles: Exodus by American author JJ Clayborn.[9]

    References

    1. ↑ "Epsilon Tauri b". NASA Exoplanet Archive. Retrieved 28 July 2016.
    2. 1 2 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.
    3. ↑ NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars. IAU.org. 9 July 2014
    4. ↑ "NameExoWorlds The Process". Archived from the original on 2015-08-15. Retrieved 2015-09-05.
    5. ↑ Final Results of NameExoWorlds Public Vote Released, International Astronomical Union, 15 December 2015.
    6. ↑ "NameExoWorlds The Approved Names". Archived from the original on 2018-02-01. Retrieved 2015-12-21.
    7. ↑ Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 19 February 2011.
    8. ↑ Fraser Cain (September 15, 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011.
    9. ↑ Clayborn, JJ (March 2017), Starsong Chronicles: Exodus, ISBN 978-1520611747
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