Zeta Eridani (ζ Eridani, abbreviated Zeta Eri, ζ Eri) is a binary star in the constellation of Eridanus. 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 4.80, it is visible to the naked eye on a clear dark night. Based on parallax measurements taken during the Hipparcos mission, it is approximately 110 light-years from 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 ...

. Zeta Eridani is the primary or 'A' component of a multiple star system designated WDS J03158-0849 (the secondary or 'B' component is 14 Eridani). Zeta Eridani's two components are therefore designated WDS J03158-0849 Aa and Ab. Aa is formally named Zibal , the traditional name for the system.

Nomenclature

''ζ Eridani'' ( Latinised to ''Zeta Eridani'') is the binary star's Bayer designation. WDS J03158-0849 A is its designation in the

Washington Double Star Catalog The Washington Double Star Catalog, or WDS, is a catalog of double stars, maintained at the United States Naval Observatory. The catalog contains positions, magnitudes, proper motions and spectral types and has entries for (as of June 2017) 141, ...

. The designations of the two components as WDS J03158-0849 Aa and Ab derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by 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 ...

(IAU). Zeta Eridani bore the traditional name of ''Zibal''. This is an old misreading of the Arabic رئل ''riʼal'' "ostrich chicks" (with the carrier letter for the glottal stop taken for a 'b', and ر 'r' taken for ز 'z'), originally applied to a number of stars near Beid and Keid. In 2016, the

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 catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name ''Zibal'' for the component WDS J03158-0849 Aa on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.

Properties

Zeta Eridani is a single-lined spectroscopic binary system with an

orbital period The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...

of 17.9 days and an

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 ...

of 0.14. The primary is a mild

Am star An Am star or metallic-line star is a type of chemically peculiar star of spectral type A whose spectrum has strong and often variable absorption lines of metals such as zinc, strontium, zirconium, and barium, and deficiencies of others, such as ca ...

with a stellar classification of kA4hA9mA9V. This notation indicates this is a

main-sequence star In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hert ...

with the Ca-II K absorption line strength (k) of an A4 star, and the hydrogen lines (h) and

metallic Metallic may be a reference to: *Metal * Metalloid, metal-like substance *Metallic bonding, type of chemical bonding * Metallicity, in astronomy the proportion of elements other than helium and hydrogen in an object *Metallic color, a color that ...

lines (m) of an A9 star. It has about 185% of the

Sun's mass 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 10.3 times the Sun's radius. This is a relatively young star with an estimated age of 800 million years, and it appears to have a moderately high rotation rate with a

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 ...

of 82 km/s. The system displays a statistically significant

infrared excess An infrared excess is a measurement of an astronomical source, typically a star, that in their spectral energy distribution has a greater measured infrared flux than expected by assuming the star is a blackbody radiator. Infrared excesses are oft ...

at a wavelength of 70 μm. This suggests the presence of an orbiting

debris disk A debris disk (American English), or debris disc (Commonwealth English), is a circumstellar disk of dust and debris in orbit around a star. Sometimes these disks contain prominent rings, as seen in the image of Fomalhaut on the right. Debris di ...

. The temperature of the dust is 70 K, indicating an orbital distance of 31 AU. It has an estimated mass of about 0.26% of the Earth.

References

External links

* {{DEFAULTSORT:Zeta Eridani A-type main-sequence stars Am stars Eridanus (constellation) Zibal Eridani, Zeta Eridani, 13 020320 015197 0984 Durchmusterung objects Spectroscopic binaries