ALPHA TEL (Alpha Telescopii). The modern constellations, those that survive, honor two cognate scientific instruments, Microscopium, the Microscope and Telescopium, the Telescope, the first south of Capricornus, the latter south of neighboring Sagittarius. Neither constellation is very bright, the luminary of Telescopium barely fourth magnitude (3.51) Alpha Telescopii, which like most of the stars in modern constellations has no formal proper name. Though the brightest star of its constellation, it is nearly as obscure as the constellation itself, mentioned in only about one scientific paper a year. A class B (B3) blue subgiant (more about that below) almost exactly 250 light years away, this quite-luminous star shines with the light of almost 900 Suns from a surface heated to 18,400 Kelvin. The luminosity and temperature tell that the star has a mass six times that of the Sun. In opposition to the subgiant spectral class, which suggests that the star is beginning to evolve from being a core-hydrogen-fusing dwarf, the luminosity and temperature strongly suggest that the Alpha Tel is fairly young and has a long way to go before any kind of evolution sets in. The star seems decidedly single. Its most significant characteristic, other than being a rather hot class B star, is that of chemical peculiarity. There are several classes of such stars in which various chemical elements are enriched or depleted as a result of diffusion of atoms (some settling below the star's gaseous surface, others lofted upward by radiation, the effect sometimes coupled with magnetic fields). The most prominent are the "Am" metallic line stars (Sirius, for example), the "Ap" (for "class A peculiar," like Cor Caroli and Alioth) stars that have strong magnetic fields, and the "mercury-manganese stars" (Alpheratz), which obviously have enhancements of these elements. Alpha Tel is a member of the rare class of "helium-rich stars" whose oddness is also diffusion- related. (Many highly evolved stars, like the Wolf-Rayet companion in Regor, are much more helium-enriched as a result of the loss of their hydrogen-rich envelopes; Alpha Tel is not one of these.) Otherwise its composition seems more-or-less normal. For a class B star, it is rotating slowly, only 35 kilometers per second (suggesting that its pole is more-or-less pointing at us). Some 7 million years from now, it really will lose its outer hydrogen layers and become a massive white dwarf like Sirius-B.
Written by Jim Kaler. Return to STARS.