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ALIFA AL FARKADAIN

(Zeta Ursae Minoris). Many stars carry multiple names. The front bowl stars of the Little Dipper of Ursa Minor are best known as Kochab (Beta UMi) and Pherkad (Gamma), but in Arabia Beta was also called both Nair al Farkadain and Anwar al Farkadain, together meaning "the bright one" and "the lights" of the "two calves," while Pherkad was Alifa al Farkadain, the "dim one of the two calves." Anwar and Alifa (al Farkadain) were subsequently and erroneously transferred to Eta and Zeta Umi, in spite of the fact that Eta is the fainter of the two (all according to Allen). Since Beta and Gamma already have perfectly good names, here we let Zeta and Eta have their alternatives. Alifa (etc.), rather Zeta, an easier term, is one of the more neglected of stars, rather odd since at fourth magnitude (4.32) it is decently bright (ranking fourth in the Little Dipper) and since it is but 12 degrees from the pole always visible from most of the northern hemisphere. It is the subject of a mere 17 scientific references over the past 20 years. This white class A (A3, rarely A1) dwarf shines with a luminosity 200 times that of the Sun from a distance of 375 light years, the one measure of temperature a consistent 8700 Kelvin. Such a high luminosity is anomalous for an A3 dwarf. Visually, the star is over two magnitudes brighter than it "ought" to be, which carries it well out of hydrogen-fusing dwarfhood and into the realm of the giant stars. A closer comparison with theory reveals that this 3.4 solar mass star is right at the edge of giving up its hydrogen fusion and is about to become a true giant with a dead helium core. Some 280 million years ago, it began life as a bluer B7 dwarf. Zeta is a particularly fast rotator. The equatorial velocity is measured at 206 kilometers per second, which with a calculated radius 6.2 times larger than the Sun gives a rotation period less than 1.5 days (as opposed to the Sun's 25 days). There is some evidence that Zeta is a slightly variable, pulsating "Delta Scuti" star that subtly changes its magnitude, though no one has confirmed it. There is no evidence for duplicity. From here, Polaris (Alpha UMi) shines at mid-second magnitude. Since Zeta UMi lies close to the direction of Polaris and is 88 percent Polaris's distance, from Zeta Polaris would be almost as bright as Sirius is in our sky.