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KAFFALJIDHMA

(Gamma Ceti). If you think that is a long name, it is a reduction; the full version is "Al Kaff al Jidhmah." Of obvious Arabic origin, the name originally referred to the whole circlet of stars that makes the head of Cetus, the Whale, was applied at one time to Menkar, the Alpha star, and is now applied to the Gamma star that lies at the point where the Whale's head joins the neck. Like so many Arabic names, however, it actually refers back to an original Arabic constellation, and means "Part of a Hand," the stellar circlet perhaps representing a hand's palm or outstretched fingers. At the faint end of third magnitude (3.47), and fourth brightest star in the constellation (ignoring variable Mira), Kaffaljidhma is just barely exceeded in brightness by Eta (7th letter in the Greek Alphabet) Ceti. Physically, Kaffaljidhma is an ordinary white main-sequence class A (A3) star with an ill-defined surface temperature around 8700 K. From that and its nearby distance of only 82 light years we find a luminosity 19 times that of the Sun and a mass just about double solar. Its high rotation speed of 183 kilometers per second keeps the atmosphere stirred and of normal composition (that is, not "chemically peculiar."). The star's claim to any fame is its triple nature. It is first an easily viewed classic double. Kaffaljidhma proper (the "A" component, by itself magnitude 3.56) is accompanied 2.8 seconds of arc away by a dimmer sixth magnitude (6.25) and cooler class F (F3) companion with a luminosity and mass respectively 1.6 and 1.3 times that of the Sun. The two are sometimes taken as "blue and yellow" through the telescope, but that is certainly a visual contrast effect, as the fainter "B" companion is only a bit yellower than the main star. They are separated by at least 70 astronomical units and have an orbital period of at least 320 years. Far far away (nearly a quarter of a degree!) lies a tenth magnitude (10.1) cooler class K (K5) companion that shares the motion of the two and is most likely a gravitational member. If so, this 0.6 solar mass orange star, with a luminosity only a tenth solar, lies at least 21,000 astronomical units away from the close double and takes at least 1.5 million years to make a circuit. From Kaffaljidhma proper, the dim "C" component would shine at magnitude -1.9, about the same as Sirius does in our sky. From dim "C", the double would be easily separable by the naked eye as two brilliant stars, one about as bright as our Venus, the other 20 times more. All three are ordinary hydrogen-fusing dwarfs. The outer companion is so far away that it will almost certainly escape to wander free, while the inner double will someday become a double white dwarf.