What is the physical reason that astronomers can find the luminosity class (I,II,III,IV,or V)of a star using the star's spectrum?
A) The relative amounts of hydrogen,helium,and other elements are different for stars of different luminosity classes.
B) The absorption lines in the spectrum are affected by the density and pressure of the star's atmosphere.
C) The absorption lines in the spectrum are affected by the star's surface temperature.
D) The wavelength of maximum emission (given by Wien's law)is affected by the size of the star.

Question

Quizplus · Accepted Answer

The absorption lines in the spectrum are affected by the density and pressure of the star's atmosphere, which is related to its luminosity class. Stars of different luminosity classes have different atmospheric conditions, which are reflected in their spectra. Therefore, by analyzing the absorption lines in a star's spectrum, astronomers can determine its luminosity class.

What Is the Physical Reason That Astronomers Can Find the Luminosity