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!