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KAKKAB
(Alpha Lupi). Don't take the proper name too seriously:it's only partial and no one ever uses it anyway. According to R.H. Allen, the full name, apparently from the ancient EuphratesValley, is "Kakkab Su-gub Gud-Elim," meaning "the Star Left of theHorned Bull" (Centaurus). Far better to know it by its Greekletter name Alpha Lupi (the luminary of Lupus, the Wolf). This blue-white second magnitude(2.30) star lies in one of the most southerly of all the ancientconstellations. Shining south of Scorpius, the figure is hardly known in the north, butfrom southern latitudes it is glorious, Alpha Lupi bright eventhough 550 light years away. A hot, class B (B1.5) giant, AlphaLupi pours 18,000 solar luminosities (most of it in the invisibleultraviolet) into space from a 21,600 Kelvin surface with a radiusnearly 10 times that of the Sun. Like agreat many hot O and B stars, "Kakkab" is a member of a looselyorganized grouping, an "OB association." Huge numbers of themflock the Galaxy. Alpha Lupi is a member of the subassociation"Upper Centaurus-Lupus," or UCL, which in turn is a part of a hugesuper-collection called the Scorpius-Centaurus Association. Fromanalysis of all its members, UCL lies at an average distance of 450light years, which fits in very nicely with our star's individuallymeasured distance of 550. As are many hot class B giants, AlphaLupi is a "Beta Cephei star," one exemplified by Mirzam, Beta Canis Majoris. These are allsubtle variables that pulsate with multiple periods. With a majoroscillation cycle of 0.259847 days (the periods really known tosuch accuracy, to the fraction of a second), in which it varies byonly 0.03 magnitudes (about 3 percent), Alpha Lupi has one of thelongest periods of its class. A secondary pulsation takes 0.236798days. A 13th magnitude "companion" 28 seconds of arc away maybelong to Kakkab or may just be in the line of sight. As aspectrally-classed giant star, Alpha Lupi has probably just ceasedits core hydrogen fusion. At 10 to 11 solar masses, the star -- amere 20 million years old -- is just on the dividing line of thosethat will blow up and those that will turn into massive neon-oxygenwhite dwarfs.