The spectrum of a very distant source shows spectral absorption lines of ionized helium, He II, and molecular absorption bands from titanium oxide, TiO. What could one conclude about this star?
A) The source is probably the spectrum of a binary system, two stars close together, a hot star and a cooler companion, unresolved as separate stars from Earth but contributing separate spectra.
B) The source must have a very hot atmosphere containing helium gas overlying a much cooler stellar surface.
C) The source must have a thick, cool atmosphere overlying a hot stellar atmosphere.
D) There must be cool, interstellar gas containing TiO between the star and Earth.

Question

Quizplus · Accepted Answer

The presence of spectral absorption lines from both ionized helium (He II), which indicates a very hot star, and molecular absorption bands from titanium oxide (TiO), which indicates a much cooler atmosphere, suggests that the source is likely a binary system. This system would consist of a hot star (responsible for the ionized helium lines) and a cooler companion star (responsible for the TiO bands), which are unresolved from Earth, appearing as a single point of light but contributing separate spectra.

The Spectrum of a Very Distant Source Shows Spectral Absorption