Epsilon Tauri b (abbreviated ε Tauri b or ε Tau b), formally named Amateru , is a

super-Jupiter A super-Jupiter is a gas giant exoplanet that is more massive than the planet Jupiter. For example, substellar companion, companions at the planet–brown dwarf borderline have been called super-Jupiters, such as around the star Kappa Andromedae. ...

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...

orbiting the K-type

giant star A giant star has a substantially larger radius and luminosity than a main-sequence (or ''dwarf'') star of the same surface temperature. They lie above the main sequence (luminosity class V in the Yerkes spectral classification) on the Hertzsp ...

Epsilon Tauri Epsilon Tauri or ε Tauri, formally named Ain (), is an orange giant star located approximately from the Sun in the constellation of Taurus. An exoplanet (designated Epsilon Tauri b, later named Amateru) is believed to be orbiting the ...

approximately away from the

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

Taurus Taurus is Latin for 'bull' and may refer to: * Taurus (astrology), the astrological sign ** Vṛṣabha, in vedic astrology * Taurus (constellation), one of the constellations of the zodiac * Taurus (mythology), one of two Greek mythological ch ...

. It orbits the star further out than Earth orbits the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

. It has moderate

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-Centre (geometry), center, in geometry * Eccentricity (g ...

. The planet orbits one of the four giant stars in the

Hyades Hyades may refer to: *Hyades (band) *Hyades (mythology) *Hyades (star cluster), an open star cluster in the constellation Taurus {{Disambiguation it:Iadi ...

star cluster, and was the first planet ever discovered in an

open cluster An open cluster is a type of star cluster made of tens to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, and ...

Name

In July 2014, the

International Astronomical Union The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...

(IAU) launched

NameExoWorlds NameExoWorlds (also known as IAU NameExoWorlds) were various projects managed by the International Astronomical Union (I.A.U.) to encourage names to be submitted for astronomical objects, notably exoplanets. The accepted names would later be cons ...

, a process for giving proper names to certain exoplanets. The process involved public nomination and voting for the new names. In December 2015, the IAU announced the winning name was Amateru for this planet. The name was based on that submitted by the Kamagari Astronomical Observatory of

Kure is a city in the Hiroshima Prefecture, Japan. , the city had an estimated population of 208,024 in 106,616 households and a population density of 590 persons per km2. The total area of the city is . With a strong industrial and naval heritage, ...

, Hiroshima Prefecture,

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

: namely '

Amaterasu , often called Amaterasu () for short, also known as and , is the goddess of the sun in Japanese mythology. Often considered the chief deity (''kami'') of the Shinto pantheon, she is also portrayed in Japan's earliest literary texts, the () ...

', the

Shinto , also called Shintoism, is a religion originating in Japan. Classified as an East Asian religions, East Asian religion by Religious studies, scholars of religion, it is often regarded by its practitioners as Japan's indigenous religion and as ...

goddess of the Sun, born from the left eye of the god

Izanagi Izanagi (イザナギ/伊邪那岐/伊弉諾) or Izanaki (イザナキ), formally referred to with a divine honorific as , is the creator deity (''kami'') of both creation and life in Japanese mythology. He and his sister-wife Izanami are the ...

. The IAU substituted 'Amateru' - which is a common Japanese

appellation An appellation is a legally defined and protected geographical indication used to identify where the ingredients of a food or beverage originated, most often used for the origin of wine grapes. Restrictions other than geographical boundaries, s ...

for

shrines A shrine ( "case or chest for books or papers"; Old French: ''escrin'' "box or case") is a sacred space dedicated to a specific deity, ancestor worship, ancestor, hero, martyr, saint, Daemon (mythology), daemon, or similar figure of respect, wh ...

when they enshrine Amaterasu - because 'Amaterasu' is already used for asteroid 10385 Amaterasu.

Characteristics

Mass, radius and temperature

Epsilon Tauri b is a "

", an exoplanet that has a mass larger than that of the gas giants

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...

and

Saturn Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a gas giant, with an average radius of about 9 times that of Earth. It has an eighth the average density of Earth, but is over 95 tim ...

. It has a temperature of . It has a

minimum mass In astronomy, minimum mass is the lower-bound calculated mass of observed objects such as planets, stars, binary systems, nebulae, and black holes. Minimum mass is a widely cited statistic for extrasolar planets detected by the radial velocit ...

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

Host star

The planet orbits a ( K-type)

named

. It has exhausted the

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

supply in its core and is currently fusing helium. The star has a mass of 2.7 and a radius of around 12.6 . 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 and has a surface temperature of 5778 K. The star's

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

, 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 ) every 586 days at a distance of 1.88 AU (compared to

Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

' orbital distance from the Sun, which is 1.52 AU). It has a mildly eccentric orbit, with an eccentricity of 0.08.

Discovery

Epsilon Tauri b was discovered by using the High Dispersion Echelle Spectrograph at

Okayama Astrophysical Observatory The (NAOJ) is an astronomy, astronomical research organisation comprising several facilities in Japan, as well as an observatory in Hawaii and Chile. It was established in 1988 as an amalgamation of three existing research organizations - the To ...

(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. 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. These values were later refined to a period of 586 days and an eccentricity of 0.08.

In popular culture

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

References

External links

* {{Sky, 04, 28, 37.0, +, 19, 10, 50 Taurus (constellation) Giant planets Exoplanets discovered in 2007 Exoplanets detected by radial velocity Exoplanets with proper names Hyades (star cluster)