Beta Eridani (β Eridani, abbreviated Beta Eri, β Eri), formally named Cursa , is the second-brightest

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 ...

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 ...

of Eridanus, located in the northeast end of this constellation near the shared border with Orion. The apparent visual magnitude of this star is 2.796, so it can be viewed with the naked eye in dark skies.

Parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...

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 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 ...

Nomenclature

''Beta Eridani'' 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 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 and Tau Orionis. According to a NASA catalogue of stars, ' was the title of three stars: β Eri is ''Cursa'', Psi Eridani ', and Lambda Eridani ' (excluding Tau Orionis). 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 (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, (), "the Jade Well", refers to an asterism consisting of β Eridani, λ Eridani, ψ Eridani and τ Orionis. Consequently, the Chinese name 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 of A3 III, with the luminosity class III indicating that this is a giant star which has consumed the hydrogen at its core and evolved away from 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 ...

. The

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 the outer envelope is about 8,360 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 bu ...

is a rapid , compared to along the Sun's

equator The equator is the circle of latitude that divides Earth into the Northern Hemisphere, Northern and Southern Hemisphere, Southern Hemispheres of Earth, hemispheres. It is an imaginary line located at 0 degrees latitude, about in circumferen ...

. The star is known to vary in apparent visual magnitude, 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 star with an apparent magnitude 10.90 at an angular separation of 120

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 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 Celestial pole, north celestial pole (NCP), turning pos ...

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 TIC objects