Which atom or ion produces strong absorption lines in the spectra of stars with relatively cool surface temperatures?
A) TiO, molecules of titanium oxide
B) Mg II, ionized magnesium
C) Ca II, ionized calcium
D) He I, neutral helium

Question

Quizplus · Accepted Answer

TiO molecules produce strong absorption lines in the spectra of stars with relatively cool surface temperatures (typically M, K, and some late G-type stars). Such stars have effective temperatures below 5000 K, resulting in the presence of molecules in their atmospheres, including TiO. Mg II and Ca II are more commonly observed in hotter stars, while He I is often seen in hotter and intermediate temperature stars.

Which Atom or Ion Produces Strong Absorption Lines in the Spectra