Absorption-line strengths are used in the spectral classification of stars and the determination of surface temperatures.Which atomic or molecular constituent exhibits strong absorption lines in spectra from stars with very high surface temperature?
A) H
B) Ca II
C) He II
D) TiO

Question

Quizplus · Accepted Answer

He II (ionized helium) exhibits strong absorption lines in the spectra of stars with very high surface temperatures. In fact, the presence of He II lines in a star's spectrum is often used as an indicator of its temperature. The other choices (H, Ca II, and TiO) are all associated with cooler stars and have weaker or no absorption lines at high temperatures.

Absorption-Line Strengths Are Used in the Spectral Classification of Stars