Epsilon Tauri or ε Tauri, formally named Ain (), is an

orange giant 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 Hertzspr ...

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

located approximately from 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 ...

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 ...

. An

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 ...

(designated Epsilon Tauri b, later named Amateru) is believed to be orbiting the star. It is a member of the

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

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 ...

. As such its age is well constrained at 625 million years. It is claimed to be the heaviest among planet-harboring stars with reliable initial masses. Given its large mass, this star, though presently of

spectral type In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

K0 III, was formerly of spectral type A that has now evolved off the

main sequence In astronomy, the main sequence is a classification of stars which appear on plots of stellar color index, color versus absolute magnitude, brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or d ...

into the giant phase. It is regarded as a red clump giant; that is, a core-helium burning star. Since Epsilon Tauri lies near the plane of the

ecliptic The ecliptic or ecliptic plane is the orbital plane of Earth's orbit, Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making. Fr ...

, it is sometimes

occulted An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks f ...

by the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

and (very rarely) by

planet A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...

s. It has an 11th magnitude companion 182

arcsecond A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of a degree. Since one degree is of a turn, or complete rotation, one arcminute is of a tu ...

s from the primary, although this is an unrelated background star.

Nomenclature

''ε Tauri'' ( Latinised to ''Epsilon Tauri'') is the star's

Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek alphabet, Greek or Latin letter followed by the genitive case, genitive form of its parent constellation's Latin name. The original list of Bayer design ...

; it also bears the

Flamsteed designation A Flamsteed designation is a combination of a number and constellation name that uniquely identifies most naked eye stars in the 88 modern constellations, modern constellations visible from southern England. They are named after John Flamsteed, au ...

of 74 Tauri. On discovery, the planet was designated Epsilon Tauri b (or Ain b). The star bore the traditional name ''Ain'' (

Arabic Arabic (, , or , ) is a Central Semitic languages, Central Semitic language of the Afroasiatic languages, Afroasiatic language family spoken primarily in the Arab world. The International Organization for Standardization (ISO) assigns lang ...

''عين'' for "eye") and was given the name ''Oculus Boreus'' (

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

for "Northern eye") by

John Flamsteed John Flamsteed (19 August 1646 – 31 December 1719) was an English astronomer and the first Astronomer Royal. His main achievements were the preparation of a 3,000-star catalogue, ''Catalogus Britannicus'', and a star atlas called '' Atlas ...

. In 2016, 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 ...

organized a

Working Group on Star Names The International Astronomical Union (IAU) established a Working Group on Star Names (WGSN) in May 2016 to catalog and standardize proper names for stars for the international astronomical community. It operates under Division C – Education ...

(WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included ''Ain'' for this star. In July 2014, the

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 winning 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 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 for

shrine A shrine ( "case or chest for books or papers"; Old French: ''escrin'' "box or case") is a sacred space">-4; we might wonder whether there's a point at which it's appropriate to talk of the beginnings of French, that is, when it wa ...: ''escri ...

s when they enshrine Amaterasu – because 'Amaterasu' is already used for an asteroid ( 10385 Amaterasu). In Chinese, (), meaning '' Net'', refers to an asterism consisting ε Tauri, δ³ Tauri, δ¹ Tauri, γ Tauri,

Aldebaran Aldebaran () is a star in the zodiac constellation of Taurus. It has the Bayer designation α Tauri, which is Latinized to Alpha Tauri and abbreviated Alpha Tau or α Tau. Aldebaran varies in brightness from an apparent vis ...

, θ² Tauri, 71 Tauri and λ Tauri. Consequently, the

Chinese name Chinese may refer to: * Something related to China * Chinese people, people identified with China, through nationality, citizenship, and/or ethnicity **Han Chinese, East Asian ethnic group native to China. **'' Zhonghua minzu'', the supra-ethni ...

for ε Tauri itself is (), "the First Star of Net".香港太空館 – 研究資源 – 亮星中英對照表
, Hong Kong Space Museum. Accessed on line November 23, 2010.

Planetary system

In 2007, a massive

was reported orbiting the star with a period of 1.6 years in a somewhat eccentric orbit. It was the first planet ever discovered in an open cluster. A 2023 study updated this planet's parameters, and detected additional

radial velocity The radial velocity or line-of-sight velocity of a target with respect to an observer is the rate of change of the vector displacement between the two points. It is formulated as the vector projection of the target-observer relative velocity ...

variations that are likely caused by stellar activity.

References

External links

* * {{DEFAULTSORT:Epsilon Tauri K-type giants Horizontal-branch stars Planetary systems with one confirmed planet Hyades (star cluster) Taurus (constellation) Tauri, Epsilon

1409 Year 1409 ( MCDIX) was a common year starting on Tuesday of the Julian calendar. Events January–March * January 1 – The Welsh surrender Harlech Castle to the English. * January 18 – The Decree of Kutná Hora strengthe ...

BD+18 0640 Tauri, 074 028305 020889 17554529

Ain Ain (, ; ) is a French department in the Auvergne-Rhône-Alpes region, Eastern France. Named after the Ain river, it is bordered by the Saône and Rhône rivers. Ain is located on the country's eastern edge, on the Swiss border, where it ...