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]

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]

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 M_J and a potential radius of around 18% larger than Jupiter (1.18 R_J, or 12 R_🜨) based on its mass, since it is more massive than the jovian planet.

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.

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.

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.

• 4 Ursae Majoris b
• Epsilon Eridani b
• Epsilon Reticuli Ab

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

• "Notes for planet eps Tau b". Extrasolar Planets Encyclopaedia. Retrieved 2008-06-24.