GAMMA VOL (Gamma Volantis). Though deemed "obscure" from the
northern hemisphere, Volans (the Flying
Fish) is one of the fainter mainstays of the southern, as it is
close enough to the southern pole to be circumpolar from roughly
the Tropic of Capricorn and south. It is an attractive kite-shaped
figure whose main stars are all so much about the same brightness
that it is hard to tell which is the luminary. The prize, such as
it is, goes to just-barely-fourth magnitude (3.60) Gamma Volantis,
which is a bit of a cheat, since the star is a wide double
(separation now 14.1 seconds of arc) made of Gamma-1 Vol (the
western one, at magnitude 5.67) and Gamma-2 (the eastern, at 3.78).
If taken separately, Beta Vol is the winner (as stated by Allen in
his "star names" book). But the pair is inseparable by the naked
eye, and they add together to beat out Beta. Alpha comes in at
number 3. Taken in order of brightness, Gamma-2 and Gamma-1 are
respectively a rather standard orange class K (K0) giant of the
kind that makes so much of our constellation patterns and a white
class F (F2) dwarf, the color contrast making them an attractive
pair. There are no temperature measures of either one, but from
their spectral classes they should be (in the same order) 4700 and
7000 Kelvin. From the distance of 142 light years, they shine at
respective luminosities of 71 and 7.9 times that of the Sun, which give radii of 12.8 and 1.9 solar and
masses of 2.5 and 1.6 solar. Direct measure of angular diameter of
Gamma-2 yields a radius 12.7 solar, right on the mark. Gamma-1 is
an ordinary hydrogen fusing dwarf, while Gamma-2 is a stable helium
fusing "clump" giant (as it is clumped in characteristics with so
many other stars). The age of the system falls between 600 and 700
million years. Not for another 1.5 billion years will Gamma-1 make
the break to become a giant like its larger companion, by which
time Gamma-2 will have become a small white dwarf. Gamma-1 was
suspected of being a spectroscopic binary, but is more likely a
slightly unstable pulsating variable, a condition that affects a
number of dwarfs in this temperature range. While some orbital
motion is detected (the two have become 1.6 seconds of arc closer
over the past 150 or so years), there is nowhere enough information
to construct the actual orbit. Given the projected separation of
600 Astronomical Units and the estimated masses, the orbital period
must be at least 7500 years. At the projected distance, from
Gamma-2, Gamma-1 would shine at about the brightness of our full
Moon, while from Gamma-1, Gamma-2 would be nearly 6 times brighter.
(That the total luminosity ratio is greater is the result of taking
invisible infrared radiation from Gamma-2 into account.)