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ALKALUROPS (Mu Bootis). The naming of stars sometimes seemsrandom. Some bright stars within a constellation will carry noproper names, while other much fainter ones do (the classic casethat ofGamma Cassiopeiae). InBootes, the Herdsman, the Alpha, Beta, andGamma stars carry the proper namesArcturus,Nekkar, andSeginus. Third magnitude Delta has none,but then we can reach all the way to fourth magnitude (4.31) MuBootis, which is called by the jaw-breaking name Alkalurops. Oncewe get away from the first magnitude stars, naming has more to dowith position than brightness. "Alkalurops" actually derives fromGreek, and means "club." But the original, going from Greek toArabic 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 arcaway from the star is a sixth (6.50) magnitude companiontechnically visible to the naked eye. The principal star,Alkalurops proper (Alkalurops A), is a mid-temperature (7195Kelvin) class F(F0) dwarf. At a distance of 120 light years, itradiates 20 solar luminosities, which makes it too bright for itsclass, implying that it is either starting to evolve or that it toois double. The spectrum suggests an unresolved companion with aperiod near 300 days (making the system quadruple). The star mayalso be a subtle variable. The easily-visible companion(Alkalurops BC), however, is clearly double, and consists of a pairof sunlike (class G1) dwarf stars that average 1.5 seconds of arcapart. The seventh magnitude (6.98) brighter star (Alkalurops B)has double the solar luminosity, whereas the fainter seventhmagnitude companion (Alkalurops C, 7.63) is almost a solar clone. The two orbit each other every 260 years at an average distance of54 Astronomical Units (35 percent farther than Pluto is from theSun). The smaller pair lies at least 4000 AU distant from two-solar mass (or so) Alkalurops A and takes at least 125,000 years tomake a full circuit. From Alkalurops A, the BC pair would appearas a brilliant "double sun" (at that distance, however, starlike)100 times or so brighter than our Venus, separated by up to adegree apart. Alkalurops A lies near a critical stellar transitionpoint. Hotter stars fuse hydrogen to helium through the carboncycle (in which carbon is used as a nuclear catalyst) rather thandirectly, have no circulating convective outer layers, and alsotend to rotate much faster (Alkalurops spinning at least 40 timesfaster than theSun).
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