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ADHAFERA (Zeta Leonis). The Sickle ofLeois known for the bright starRegulus andthe famous doubleAlgieba. Just aboveAlgieba, you can admire a fainter star, third magnitude (but justbarely so, 3.44) Adhafera. The name, which comes directly fromArabic and means "the lock of hair," makes sense, as the star liesin Leo's great mane. Unfortunately, however, "Adhafera" actuallyrefers to nearbyComa Berenices(Berenices Hair), and was given to Leo's star in error, a commonfailing of those who applied star names. Adhafera, a yellow-whiteclass F (F0) giant star 260 light years away, actually shines 207times more brightly than does theSun. Witha temperature of 7030 Kelvin, almost all of its radiation pours out inthe visible, where we can see it (that is, there is almost nocorrection for invisible ultraviolet or infrared, quite like ourSun), from which we find a radius 10 times solar. Spinning with anequatorial velocity of 84 kilometers per second (48 times solar),this three solar mass star takes less than six days to make a fullrotation. Adhafera's real interest lies in its very clean state ofevolution. Class F giants are rare, as they are making aremarkably fast transition from the main sequence (where they oncefused hydrogen to helium in their cores) to the giant state (wherethey will eventually fuse helium to carbon). Only a million yearsago, Adhafera was a white class A (almost class B) dwarf. Now witha shrinking, dead helium core, it will become an orange class Kgiant star in only another million years, and will then make its"run to the top," taking a leisurely 100 million years to expandfrom 12 solar radii to a red class M giant with a radius nearthat of the Earth's orbit! At that point, it will fire up itshelium and settle down for a time again as a smaller orange giant. Also called 36 Leonis, Adhafera has a sixth magnitude "companion"(35 Leonis) 5 minutes of arc away. Alas, it is just a line ofsight coincidence, 35 Leonis being only 100 light years away, lessthan half Adhafera's distance, the two moreover going in differentdirections. The fainter star is not without its interest, however. A class G (G1.5) dwarf-subgiant, 35 Leonis has the same surfacetemperature and color as does the Sun. Just beginning itsevolution to the giant state, it is more massive and 3.5 times asluminous.
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