Gamma Eridani

γ Eridani

Template:Location mark Location of γ Eridani (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Eridanus
Right ascension	Template:RA
Declination	Template:DEC
Apparent magnitude (V)	2.88 - 2.96
Characteristics
Evolutionary stage	AGB
Spectral type	M0III-IIIb
U−B Template:Engvar	+1.96
B−V Template:Engvar	+1.58
Variable type	Lb?
Astrometry
Radial velocity (Rv)	km/s
Proper motion (μ)	RA: +61.57 mas/yr Dec.: −113.11 mas/yr
Parallax (π)	17.0016±0.2254 mas
Distance	Template:Rnd ± Template:Rnd ly (Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)	−1.19
Details
Mass	1.55 Template:Solar mass
Radius	Template:Solar radius
Luminosity	Template:Solar luminosity
Surface gravity (log g)	1.52 cgs
Temperature	K
Metallicity [Fe/H]	+0.00 dex
Rotational velocity (v sin i)	3.8 km/s
Metallicity [Fe/H]	{{{metal_fe2}}} dex
Other designations
Template:Odlist
Database references
SIMBAD	data

Gamma Eridani (γ Eridani, abbreviated Gamma Eri, γ Eri), formally named Zaurak Template:IPAc-en, 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 at a distance of about 203 light years from the Sun, as determined by the Hipparcos astrometry satellite.

Description

File:GammaEriLightCurve.png

A light curve for Gama Eridani, plotted from Hipparcos data

Gamma Eridani has been defined as a standard star for the spectral class M0III-IIIb. It is a red giant on the asymptotic giant branch, fusing hydrogen and helium in separate shells outside its core. Observations published in 1960 showed it to vary in brightness by a few hundredths of a magnitude. In 1977, it was officially listed as a variable star in the General Catalogue of Variable Stars although the class of variable is uncertain.

The Gaia EDR3 data identified a comoving companion star of Gamma Eridani, at a projected separation of . It is likely that there is an additional red dwarf companion that at a distance within , too close to resolve from the primary.

Nomenclature

Gamma Eridani is the star's Bayer designation. It has the traditional name Zaurak, alternatively spelled Zaurac, which is one of the Arabic words for 'boat'. In 2016, the International Astronomical Union 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 Zaurak for this star.

In Chinese, (), meaning Celestial Meadows, refers to an asterism consisting of γ Eridani, δ Eridani, π Eridani, ε Eridani, ζ Eridani, η Eridani, π Ceti, τ¹ Eridani, τ² Eridani, τ³ Eridani, τ⁴ Eridani, τ⁵ Eridani, τ⁶ Eridani, τ⁷ Eridani, τ⁸ Eridani and τ⁹ Eridani. Consequently, the Chinese name for γ Eridani itself is (, Template:Langx.)

USS Zaurak (AK-117) was a United States Navy Crater class cargo ship named after the star.