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.