Epsilon Tauri b

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]

Epsilon Tauri b
Artistic simulation of Epsilon Tauri b orbiting its host star.
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)

    The planet orbits one of the four giant stars in the Hyades cluster that is 2.7 times the mass of our Sun, making it the most massive planet-harboring star. This provides evidence that it was an A-type star when it was on the main-sequence.

    Name

    In July 2014, the International Astronomical Union (IAU) launched 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. 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
    5. Final Results of NameExoWorlds Public Vote Released, International Astronomical Union, 15 December 2015.
    6. NameExoWorlds The Approved Names
    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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