Here we have four telescopes, each pointed at a different star. The light from
each star is directed through a prism to produce a spectrum. Each of the
spectra has a set of absorption lines created by the presence of hydrogen in
the stars' atmospheres.
Order the spectra, starting with the one that is moving the fastest toward us
and ending with the one that is moving the fastest away from us. What sequence
do you come up with?
To see the answer scroll down to the bottom of this page.
