ALKALUROPS (Mu Bootis). The naming of stars sometimes seems
random. Some bright stars within a constellation will carry no
proper names, while other much fainter ones do (the classic case
that of Gamma Cassiopeiae). In Bootes, the Herdsman, the Alpha, Beta, and
Gamma stars carry the proper names Arcturus, Nekkar, and Seginus. Third magnitude Delta has none,
but then we can reach all the way to fourth magnitude (4.31) Mu
Bootis, which is called by the jaw-breaking name Alkalurops. Once
we get away from the first magnitude stars, naming has more to do
with position than brightness. "Alkalurops" actually derives from
Greek, and means "club." But the original, going from Greek to
Arabic to Latin to Greek to Latin and thence made to sound Arabic,
came to mean "shepherd's staff," more fitting for the Herdsman.
Alkalurops is a wonderful triple star. Lying 1.8 minutes of arc
away from the star is a sixth (6.50) magnitude companion
technically visible to the naked eye. The principal star,
Alkalurops proper (Alkalurops A), is a mid-temperature (7195
Kelvin) class F(F0) dwarf. At a distance of 120 light years, it
radiates 20 solar luminosities, which makes it too bright for its
class, implying that it is either starting to evolve or that it too
is double. The spectrum suggests an unresolved companion with a
period near 300 days (making the system quadruple). The star may
also be a subtle variable. The easily-visible companion
(Alkalurops BC), however, is clearly double, and consists of a pair
of sunlike (class G1) dwarf stars that average 1.5 seconds of arc
apart. The seventh magnitude (6.98) brighter star (Alkalurops B)
has double the solar luminosity, whereas the fainter seventh
magnitude companion (Alkalurops C, 7.63) is almost a solar clone.
The two orbit each other every 260 years at an average distance of
54 Astronomical Units (35 percent farther than Pluto is from the
Sun). The smaller pair lies at least 4000 AU distant from two-
solar mass (or so) Alkalurops A and takes at least 125,000 years to
make a full circuit. From Alkalurops A, the BC pair would appear
as a brilliant "double sun" (at that distance, however, starlike)
100 times or so brighter than our Venus, separated by up to a
degree apart. Alkalurops A lies near a critical stellar transition
point. Hotter stars fuse hydrogen to helium through the carbon
cycle (in which carbon is used as a nuclear catalyst) rather than
directly, have no circulating convective outer layers, and also
tend to rotate much faster (Alkalurops spinning at least 40 times
faster than the Sun).