ALKES (Alpha Crateris). Among the dimmest of all classical constellations is Crater, the Cup, which with Corvus, the Crow, rides the back of Hydra, the Water Serpent. The only proper name in the constellation, "Alkes" comes from Arabic and means "the wine cup," the star standing in for the whole figure (the name also clearly related to the English "alcohol.") Though mid-fourth magnitude (4.07), Alkes received the Alpha designation from Bayer. It takes second place to the un-named Delta star (that is, to Delta Crateris), and is in a virtual dead heat with Gamma Crateris. Alkes is yet one more orange class K (K0) giant star, though one with an interesting difference. At a distance of 175 light years, Alkes shines 80 solar luminosities into space from a 4725 Kelvin surface, giving the star a calculated radius 13 times that of the Sun. Alkes, with a mass estimated at around 2.5 times solar, is clearly "in the clump," a set of stars that all have about the same characteristics of luminosity and temperature and that are all fusing helium to carbon and oxygen in their cores, Arcturus and Aldebaran bright examples. Unlike most helium-burning "clump stars," unlike most stars around us, Alkes is also a modest "high velocity" star. Most of our neighbors are going around the Galaxy at a speed somewhat in excess of 200 kilometers per second. However, all the orbits are a bit different, so they drift relative to each other at speeds of 20 to 40 or so kilometers per second. From its rate of angular motion across the sky (0.48 seconds of arc per year relative to the distant background) and its speed away from us of 47 km/s, Alkes is moving relative to the Sun at 130 km/s, showing it to be a visitor from a different part of the Galaxy. The star has on occasion been placed into the group of "super-metal-rich" stars. Though the metal content is probably more solar, it is clear that the star has come to us from the inner metal-rich part of the Galaxy, the so-called "bulge." Consistently, Alkes has also been dropped into an odd category of "4150" stars, which seem to have a high abundance of cyanogen, the CN molecule. Though many stars may look alike, none is quite the same as the others!
Written by Jim Kaler. Return to STARS.