VINDEMIATRIX (Epsilon Virginis). Just over the line into third
magnitude (2.83) and third brightest in the constellation Virgo following first magnitude Spica (the Alpha star) and Porrima (Gamma), Vindemiatrix still wound
up with Bayer's Epsilon designation. The Beta star,
(Zavijava)
shines only at fourth. The name is a somewhat corrupted feminized
Latin form for the original Greek name that meant "the Grape
Gatherer," as the first visibility of the star in morning light
after the Sun cleared out of the way (the "heliacal rising") told
that it was time to pick the grapes. An alternative name derived
from Arabic, Almuredin, means the same thing, the term also
translated from the original Greek. Vindemiatrix is a somewhat
unusual star, a middling temperature (4990 Kelvin) yellow class G (G8)
giant only a bit cooler than the Sun. As a
giant, however, it is considerably brighter than the Sun. From its
temperature and distance of 102 light years, its luminosity is 83
times solar, these combining to give a radius 12 times that of the
Sun, all similar to the brighter, cooler component of Capella. The star seems to be a about 15%
richer than the Sun in metals, and is somewhat distinguished by
having most of its motion in the direction perpendicular to the
line of sight, making it appear to move rather rapidly against the
background stars, a second of arc in five years. Much more
significantly, Vindemiatrix is a rather powerful X-ray source,
implying considerable magnetic surface activity. Its total X-ray
radiation is almost 300 times that of the Sun, ranking it third
among nearby cool single giants and beat out only by Deneb Kaitos and a star called 24 Ursae
Majoris, which lies northeast of the bowl of the Big Dipper. (The double star Capella far exceeds it,
the X-radiating component unknown.) Though Vindemiatrix has surely
ceased fusing hydrogen to helium in its core, its exact internal
structure is uncertain. At three solar masses, it probably began
life as a blue-white class B star, and is now either in transition
to beginning to fire up its internal helium or has already begun to
do so.