Gamma Corvi is the brightest star in the constellation Corvus, the Crow or Raven, at magnitude 2.59. Its traditional name is Gienah; however, this name is shared with ε Cyg. To avoid confusion, the name "Gienah Corvi" may be used to distinguish γ Crv from Gienah in Cygnus.
An alternative Arabic name is "Gienah Ghurab", from Ulugh Beg's phrase "al-janah al-ghirab al-yaman", meaning "the right wing of the crow", although on modern charts γ Crv marks the left wing. Corvus is a very noticeable skewed box that crosses the sky just to the west of first magnitude Spica in Virgo. Gienah Ghurab is the right-hand star at the top of the box, and one of the "pointers" to Spica (the other is Algorab, α Crv).
Properties
Gienah Ghurab is a class B8 III blue-white giant with a temperature of 12,400 K, about the same as the much brighter supergiant Rigel in Orion. From a distance of 165 light years, γ Crv shines with a luminosity of 355 suns, and a diameter four times solar. The star is also about four times as massive as our Sun. Though an evolved giant, is still close to the main sequence. It is either in the very last stages of its core hydrogen fusion, or it has a helium core in a state of contraction. Over the next few million years, Gienah will become a red giant.
Gienah Gurab has an odd chemical composition that separates it from the more ordinary blue giants. It is a "mercury-manganese" star, like Alpheratz in Andromeda. Such stars have hugely elevated levels of these and other elements (mercury up to 100,000 times normal), while having depletions of others (such as aluminum and nickel). This chemical peculiarity is the result of the physical separation of different kinds of atoms in the stellar atmosphere, some sinking down through gravity, others lofted up by radiation. Gienah Ghurab was only identified as such a star fairly recently, because its rapid rotation speed of 150 km/sec obscures its spectrum.
[Adapted from STARS by Jim Kaler, Professor Emeritus of Astronomy, University of Illinois]