Beta Eridani (β Eridani, abbreviated Beta Eri, β Eri), formally named Cursa , is the second-brightest star in the constellation of Eridanus, located in the northeast end of this constellation near the shared border with Orion. The

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 this star is 2.796, so it can be viewed with the naked eye in dark skies. Parallax measurements yield an estimated distance of about from the

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

Nomenclature

''Beta Eridani'' is the star's Bayer designation. It has the traditional name ''Cursa'' derived from ', "the Chair (or "Footstool") of the Central One". This is the name of the star association consisting of this star along with Lambda Eridani,

Psi Eridani Psi Eridani, Latinized from ψ Eridani, is a star in the constellation Eridanus. With an apparent visual magnitude is 4.81, it can be seen with the naked eye on a clear, dark night. Based upon an annual parallax shift of 4.41 mill ...

and Tau Orionis. According to a NASA catalogue of stars, ' was the title of three stars: β Eri is ''Cursa'',

', and Lambda Eridani ' (excluding Tau Orionis). In 2016, the

International Astronomical Union The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreac ...

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 ''Cursa'' for this star. 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 ...

, (), "the Jade Well", refers to an asterism consisting of β Eridani, λ Eridani, ψ Eridani and τ Orionis. 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 ofte ...

for β Eridani itself is "the third star of Jade Well" ( ').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. In older texts, ' was also spelt '.

Properties

β Eridani has a

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 ...

of A3 III, with the

luminosity class 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 ...

III indicating that this is a

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 ...

which has consumed the hydrogen at its core and evolved away from the main sequence. The effective temperature of the outer envelope is about 8,104 K, which gives the star a white hue typical of A-type stars. The

projected rotational velocity Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface. The rotation of a star produces an equatorial bulg ...

is a rapid , compared to along the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

's equator. The star is known to vary in

, ranging between 2.72 and 2.80. A particularly strong flare up was reported in 1985. The location and trajectory of this star suggest that it is a member of the Ursa Major supergroup, an association of stars that share a common origin and motion through space. However, its photometric properties indicate that it may instead be an interloper. Beta Eridani has an

optical companion In observational astronomy, a double star or visual double is a pair of stars that appear close to each other as viewed from Earth, especially with the aid of optical telescopes. This occurs because the pair either forms a binary star (i.e. a ...

star with an apparent magnitude 10.90 at an angular separation of 120 arcseconds and a

position angle In astronomy, position angle (usually abbreviated PA) is the convention for measuring angles on the sky. The International Astronomical Union defines it as the angle measured relative to the north celestial pole (NCP), turning positive into the ...

of 148°. It has the catalogue identifier CCDM J05079-0506B.

References

{{DEFAULTSORT:Beta Eridani A-type giants Double stars Ursa Major Moving Group Cursa Eridanus (constellation) Eridani, Beta BD-05 1162 Eridani, 67 9175 033111 023875

1666 This is the first year to be designated as an ''Annus mirabilis'', in John Dryden's 1667 poem so titled, celebrating England's failure to be beaten either by the Dutch or by fire. It is the only year to contain each Roman numeral once in d ...