Epsilon Geminorum

Epsilon Geminorum (ε Geminorum, abbreviated Epsilon Gem, ε Gem), formally named Mebsuta , is a star in the constellation of Gemini, on the outstretched right 'leg' of the twin Castor. The apparent visual magnitude of +3.06 makes it one of the brighter stars in this constellation. The distance to this star can be determined by parallax measurements, giving a value of , with a margin of error of .
Nomenclature.
"ε Geminorum" (Latinised to "Epsilon Geminorum") is the star's Bayer designation. It bore the traditional names "Mebsuta", "Melboula" or "Melucta". "Mebsuta" has its roots in ancient Arabic where it and the star Mekbuda (Zeta Geminorum) were the paws of a lion. "Mebsuta" ('Mabsūṭah' مبسوطة) comes from a phrase referring to the outstretched paw. 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 "Mebsuta" for this star.
In Chinese, (), meaning "Well (asterism)", refers to an asterism consisting of ε Geminorum, μ Geminorum, ν Geminorum, γ Geminorum, ξ Geminorum, 36 Geminorum, ζ Geminorum and λ Geminorum. Consequently, ε Geminorum itself is known as (, .)
Properties.
The spectrum of this star matches a stellar classification of G8 Ib, where the luminosity class of Ib indicates this is a lower luminosity supergiant star. Alternatively, it may be a star that has passed through the asymptotic giant branch stage and possesses a detached shell of dust. The estimated mass of this star is over 19 times the mass of the Sun, and it has expanded to a radius measured at around 105–175 times that of the Sun. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.
Epsilon Geminorum is radiating around 8,500 times the luminosity of the Sun from its outer atmosphere at an effective temperature of 4,662 K. It is this temperature that gives it the yellow-hued glow of a G-type star. A surface magnetic field with a strength of has been detected on this star. This topologically complex field is most likely generated by a dynamo formed from the deep convection zone in the star's outer envelope.
Occultations.
Epsilon Geminorum lies near the ecliptic, so it can be occulted by the Moon or a planet. Such an occultation took place on April 8, 1976 by Mars, which allowed the oblateness of the planet's outer atmosphere to be measured. Epsilon Geminorum was occulted by Mercury on June 10, 1940, and on September 3, 2015 it was occulted by the asteroid Iphigenia.
In culture.
USS Melucta (AK-131) was a United States Navy Crater class cargo ship named after the star.