MULIPHEIN (Gamma Canis Majoris). The names Wezen and Hadar (in
Arabic form) were once applied to a pair of stars. Though there
are candidates, no one knows which pair. The uncertainty was in
older times expressed as an Arabic word that in part referred to a
pair of things that caused contention. The word itself was then
taken as the pair, much mangled to Muliphein (sometimes seen as
Muliphen), and then for no good reason given to the little star
that Bayer later tagged as Gamma of Canis
Major (while Wezen was given to our modern Delta, and Hadar to
modern Beta Centauri). Such is the logic of star names. The mid-
fourth magnitude (4.12) star itself, 400 light years away, is a
class B (B8) blue-white bright giant, similar in color to so many
stars in the Canis Major-Orion district.
With a temperature of 13,600 Kelvin, it radiates 685 times more
energy than the Sun and is 5 solar diameters
across. If the star were as close as its constellation-mate Sirius, it would shine in our sky almost as
brightly as Venus at her best. Muliphein's luminosity and
temperature tell of a 4.3 solar mass star that has recently ended
its hydrogen-fusing life and is now starting to evolve into a red
giant. Rotating slowly for a class B star (only 15 times the solar
rotation speed), it, like so many class B and A stars (including
Sirius), is chemically peculiar. Muliphein in particular is a
"mercury-manganese star" rather like Alpheratz in Andromeda. Muliphein is 40 percent richer in iron and
chromium (compared with hydrogen) than is the Sun, but its mercury
level is more than 2000 times solar as a result of physical lofting
of certain elements by radiation forces. The most curious thing
about the star, however, is its Gamma designation, as Muliphein is
far from being the constellation's third brightest, being beat out
by several others, including Omega! Bayer probably proceeded from
top to bottom in the constellation, as evidenced by his calling
more-southerly Adhara, the second brightest star, Epsilon. This
sort of mis-representation, however, has led some to think that
Muliphein has faded since Bayer's time (around 1600). Indeed there
is a reference that in 1670 the star disappeared and was not seen
again until 1693. Such statements have to be taken with suspicion,
however; moreover, there is no known mechanism that could cause
such an event. A dust cloud, for example, would also redden the
star, and its color is quite normal. Then again, the stars always
seem to hold surprises when we least expect them.