DENEB KAITOS (Beta Ceti).
Though the Beta star of the constellation Cetus, the
"Whale" or "Sea Monster," Deneb Kaitos
is -- at mid-second-magnitude -- (2.04) -- notably
the brightest of
a fairly hard-to-find figure. The Arabic name simply means the
"whale's tail," though that is taken from a longer phrase that
describes the star's position a bit more precisely in the southern
branch of the tail. A lesser name for the star is "Diphda," also
from Arabic and referring to a "first frog," where Fomalhaut was
the "second frog." The star is remarkably easy to find, standing
out in an otherwise lonely area south of the Great Square of
Pegasus and northeast of Fomalhaut. Like so many other naked eye
stars, Deneb Kaitos is a dying class K (K0)
giant, but like
Arcturus is a bit
warmer than most. Falling near the border of classes G and K, it
has a temperature of 4800 Kelvin. From its distance of only
96 light years (which accounts for its relative brightness), we
find a luminosity (accounting for a little infrared radiation) 145
times that of the Sun, which combined with the temperature gives us
a radius 17 times solar, large as befits a giant, but certainly not
all THAT large. Its mass is estimated to be about three times that
of the Sun. Deneb Kaitos is a remarkable enigma. It is one of the
brightest X-ray stars in the solar neighborhood, the high-energy
radiation coming from a magnetically heated corona of a few million
Kelvin rather like that belonging to the
Sun. The magnetism is
expected to be related to rotation, yet the star is rotating rather
slowly. Such high X-ray activity also suggests that it has only
recently begun to expire and still has characteristics from its
solar-like "main sequence" phase when it appeared something like
Vega and Altair and was fusing hydrogen into helium. It would
therefore have a contracting helium core. Its detailed chemical
composition, however, suggests that it has been around long enough
for its internal helium to begin to fuse to carbon. If nothing
else, Deneb Kaitos shows us that even the nearby stars are not all
that well understood.