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Spectroscopic Atlas for Amateur Astronomers 46
Table 12: Detailed spectrum of Spica (α Vir)
Overview spectrum (200L grating) and higher resolved profiles (900L grating)
Spica (260 ly) is a spectroscopic binary with an orbital period of about four days. The domi-
nant A-component is in the Giant stage and has a surface temperature of about 22,000 K,
corresponding to the spectral type B1 III-IV. The smaller B-component with the spectral
type B2V is still on the Main Sequence and with a temperature of about 18,500 K signifi-
cantly less hot and luminous. This very close orbit of the two stars causes, due to the Dop-
pler effect, a periodic splitting of spectral lines (SB2 system), which is not recognisable in
these profiles here. Ionised helium He II is here no more recognisable however still several
absorption lines of multiply ionised metals.
Line identification:
The line identification is based amongst others on [1], [51], [56], [57]
