Stars and spectra

What happens when white light is shone through a gas?

Certain specific wavelengths are absorbed, corresponding to photons with the exact energy needed to excite the gas atoms.

What is an absorption spectrum?

An absorption spectrum is a pattern where black lines correspond to wavelengths of light that have been absorbed by the gas.

What do the black lines on a star’s absorption spectrum indicate?

They correspond to wavelengths of light absorbed by the star’s atmosphere.

How can astronomers determine the elements present in a star’s atmosphere?

By examining the star’s absorption spectrum.

Into how many main categories do astronomers divide stars based on their absorption spectra?

Seven main categories, called spectral classes.

What are the Hydrogen Balmer absorption lines?

They are a set of lines that occur when hydrogen atoms absorb photons with the exact energy to excite electrons from the second energy level to higher levels.

In which stars are the Hydrogen Balmer absorption lines most prominent

In stars with temperatures around 10,000 K, corresponding to stars in spectral classes A and B.

What spectral class categories are based on?

Similarities in their absorption spectra.