MINKAR (Epsilon Corvi). Of the five prominent stars of Corvus, the Crow (or Raven), the faintest is Alchiba, oddly the Alpha star. Fourth down in brightness is Minkar, Epsilon Corvi, which is part of the prominent "box" that makes the figure. Epsilon (like Kraz, Beta Corvi) has no ancient name. But it lies adjacent to and just north of Alpha, and in modern times was apparently given the proper name "Minkar" from the alternative name for Alpha, from Allen "Al Minkar al Ghurab," "the Raven's Beak" ("Minkar" thus translated as "beak".) Such is the crooked history of star names. To the eye, Minkar almost exactly defines third magnitude (3.00). At a measured distance of 303 light years (give or take seven percent), this coolish (4230 Kelvin) class K (K2.5) giant shines with the luminosity of 930 Suns after accounting for a fair bit of infrared radiation. From temperature and luminosity, we find a respectable radius of 57 solar radii (0.26 Astronomical Units, two- thirds Mercury's orbital size), and from the theory of stellar structure and evolution, a mass close to 4 solar. A measured (and uncertain) lower limit to the equatorial rotation speed gives a maximum rotation period of 3.9 years. The star is somewhat metal-rich, the iron-to-hydrogen ratio measured at 26 percent above solar, while oxygen is up by nearly 60 percent and manganese by a factor of two. Like many of its class, it lies in the "coronal graveyard" of stars that have ceased being magnetically active via slow rotation and have developed cool outer envelopes. Minkar's evolutionary status is unclear. It might be brightening for the first time as a giant with a dead helium core (in which case it is roughly 165 million years old), it might have just fired up its helium and be dimming toward stable helium fusion, or it might have ceased helium fusion and be brightening for the second time with a dead carbon- oxygen core (in which case it is closer to 190 million years old). A small bit of lithium in the star's atmosphere suggests a nuclear process that would take place under the third option. Whatever the situation, Minkar started life as a hot class B5 star, and will die as a relatively massive white dwarf (the burnt-out stellar core) of some 0.8 solar masses, the star thus losing 80 percent of its birth weight through winds. Minkar has been classed as a mild "barium star." Full-blown barium stars have white dwarf companions, and were contaminated with nuclear by-products when the white dwarfs were mass-losing giants. There is no evidence of any companion, however, and the star probably does not really belong the barium ranks.
Written by Jim Kaler. Return to STARS.