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ALPHA APS (Alpha Apodis). One of the closest constellations to theSouth Celestial Pole (which is held byits neighbor, Octans),Apus (the Bird ofParadise) is also one of the smaller and more obscure. Itsluminary (brightest star), Alpha Apodis, shines at a mere fourthmagnitude (3.83) as do Gamma (3.89), double Delta (4.18), and Beta(4.24), not much for something as seemingly glorious as a Bird ofParadise. The obscurity is epitomized by Alpha Aps itself, as ithas only barely made a mark on the astronomical literature. Thoughclearly agiant, even theclass K spectral subclass (nominally K2.5) is uncertain, othersclaiming it to be as cool as K5. If the warmer K2.5, the star istoo "red" for its class, which can be explained by up to 0.7magnitudes of interstellar dust absorption, which is high andunrealistic for a distance of 410 light years. If at the coolerK5, the absorption is unneeded and goes away. A stated temperatureof 4256 puts the star nearer the warmer class (the cooler would be4100). If truly a K2.5 giant but with no dust absorption, the starradiates with a luminosity of 750 times that of theSun, giving a radius 49 solar. If at thecooler end of the scale, the luminosity and radius climb to 910 and60 suns, while if we go back to the warmer end and add theunrealistic 0.74 magnitudes of dust absorption, we get 1480 and 70(which are surely too high). Clearly, the star needs a lot morework, though given the common class, it's unlikely to get it. Whatever the details, Apus's chief star is a more-or-less ordinarycore-helium-fusing "clump" giant (so-called because so many otherstars have similar temperatures and luminosities) with a birth massbetween four (no interstellar absorption) and five (the maximumamount) times that of the Sun, one that began life as a hot bluedwarf of around class B5. It will eventually lose its inert outerhydrogen envelope and turn into awhite dwarf (the remnantnuclear core) with a mass around 0.8 times that of the Sun. Written byJim Kaler 4/06/07. Return toSTARS.
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