Tau² Eridani (τ² Eridani, abbreviated Tau² Eri, τ² Eri), formally named Angetenar , is a

star A star is an astronomical object comprising a luminous spheroid of plasma held together by its gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night, but their immense distances from Earth make ...

in the constellation of Eridanus. It is visible to the naked eye with an

apparent visual magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's lig ...

of 4.78. The distance to this star, as determined via the parallax method, is around 187

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 101 ...

Nomenclature

''τ² Eridani'' ( Latinised to ''Tau² Eridani'') is the system's

Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek or Latin letter followed by the genitive form of its parent constellation's Latin name. The original list of Bayer designations contained 1,564 stars. T ...

. It is one of a series of stars that share the Bayer designation Tau Eridani. It bore the traditional name ''Angetenar'', derived from the

Arabic Arabic (, ' ; , ' or ) is a Semitic language spoken primarily across the Arab world.Semitic languages: an international handbook / edited by Stefan Weninger; in collaboration with Geoffrey Khan, Michael P. Streck, Janet C. E.Watson; Walte ...

''Al Ḥināyat an-Nahr'', 'the Bend in the River', near which it lies. In 2016, the IAU 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 List of proper names of stars, proper names for stars for the international astronomical community. It operates under ...

(WGSN) to catalog and standardize proper names for stars. The WGSN approved the name ''Angetenar'' for this star on 30 June 2017 and it is now so included in the List of IAU-approved Star Names. In

Chinese Chinese can refer to: * Something related to China * Chinese people, people of Chinese nationality, citizenship, and/or ethnicity **''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation ** List of ethnic groups in China, people of v ...

, (), meaning '' Celestial Meadows'', refers to an asterism consisting of Tau² Eridani,

Gamma Eridani Gamma Eridani (γ Eridani, abbreviated Gamma Eri, γ Eri), formally named Zaurak , is a variable star in the constellation of Eridanus. It is visible to the naked eye with an apparent visual magnitude that varies around 2.9, and lies a ...

Pi Eridani Pi Eridani, Latinized from π Eridani, is a star in the constellation Eridanus. It has an apparent visual magnitude of 4.40, which is bright enough to be seen on a dark, clear night. Based upon parallax measurements, it is located roughl ...

Delta Eridani Delta Eridani, which is Latinized from δ Eridani, is a star in the equatorial constellation of Eridanus. The star is visible to the naked eye and has been observed to vary in slightly brightness between magnitudes 3.51 and 3.56, alth ...

Epsilon Eridani Epsilon Eridani ( Latinized from ε Eridani), formally named Ran, is a star in the southern constellation of Eridanus, at a declination of 9.46° south of the celestial equator. This allows it to be visible from most of Earth's surfac ...

Zeta Eridani Zeta Eridani (ζ Eridani, abbreviated Zeta Eri, ζ Eri) is a binary star in the constellation of Eridanus. With an apparent visual magnitude of 4.80, it is visible to the naked eye on a clear dark night. Based on parallax measurements t ...

Eta Eridani Eta Eridani (η Eridani, abbreviated Eta Eri, η Eri), officially named Azha (with a silent 'h', possibly ), is a giant star in the constellation of Eridanus. Based on parallax measurements taken during the Hipparcos mission, it is appr ...

, Pi Ceti, Tau¹ Eridani, Tau³ Eridani, Tau⁴ Eridani, Tau⁵ Eridani, Tau⁶ Eridani, Tau⁷ Eridani, Tau⁸ Eridani and Tau⁹ Eridani. Consequently, the

Chinese name Chinese names or Chinese personal names are names used by individuals from Greater China and other parts of the Chinese-speaking world throughout East and Southeast Asia (ESEA). In addition, many names used in Japan, Korea and Vietnam are oft ...

for Tau² Eridani itself is (, en, the Ninth Star of Celestial Meadows.)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.

Properties

Tau² Eridani is an

evolved Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation te ...

K-type

giant star A giant star is a star with substantially larger radius and luminosity than a main-sequence (or ''dwarf'') star of the same surface temperature.Giant star, entry in ''Astronomy Encyclopedia'', ed. Patrick Moore, New York: Oxford University Press ...

with a

stellar classification 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 t ...

of K0 III. It is a

red clump Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a seconda ...

giant on the

horizontal branch The horizontal branch (HB) is a stage of stellar evolution that immediately follows the red-giant branch in stars whose masses are similar to the Sun's. Horizontal-branch stars are powered by helium fusion in the core (via the triple-alpha proce ...

of the

Hertzsprung–Russell diagram The Hertzsprung–Russell diagram, abbreviated as H–R diagram, HR diagram or HRD, is a scatter plot of stars showing the relationship between the stars' absolute magnitudes or luminosities versus their stellar classifications or effective tempe ...

, indicating that is it now generating energy through the

thermonuclear fusion Thermonuclear fusion is the process of atomic nuclei combining or “fusing” using high temperatures to drive them close enough together for this to become possible. There are two forms of thermonuclear fusion: ''uncontrolled'', in which the re ...

of helium at its core. Around 660 million years old, Tau² Eridani has 2.4 times the

mass of the Sun The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass of ...

and has expanded to over 8 times the

solar radius Solar radius is a unit of distance used to express the size of stars in astronomy relative to the Sun. The solar radius is usually defined as the radius to the layer in the Sun's photosphere where the optical depth equals 2/3: :1\,R_ = 6.957 ...

. It shines with nearly 43 times the

Sun's luminosity The solar luminosity (), is a unit of radiant flux ( power emitted in the form of photons) conventionally used by astronomers to measure the luminosity of stars, galaxies and other celestial objects in terms of the output of the Sun. One nomi ...

from an outer atmosphere that has an

effective temperature The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...

of 5,049 K. It is a member of the Galactic

thin disk The thin disk is a structural component of spiral and S0-type galaxies, composed of stars, gas and dust. It is the main non-centre (e.g. galactic bulge) density, of such matter. That of the Milky Way is thought to have a scale height of around ...

population.

References

{{DEFAULTSORT:Tau2 Eridani K-type giants Horizontal-branch stars Eridanus (constellation)

Angetenar Tau2 Eridani (τ2 Eridani, abbreviated Tau2 Eri, τ2 Eri), formally named Angetenar , is a star in the constellation of Eridanus. It is visible to the naked eye with an apparent visual magnitude of 4.78. The distance to this star, as d ...

Eridani, Tau2 Durchmusterung objects Eridani, 02 017824 013288 0850