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Projects| Absorption and Emission Lines Now we can start making
the connection between the peaks and valleys we see in a star's
spectrum and the energy levels of the star's atoms. Let's say
that I shine a light with all the colors of the spectrum through
a cloud of hydrogen gas. Not all of the light will make it
through. All the photons that have exactly 10.2 eV of energy
will not make it through the hydrogen, because they will be
absorbed by hydrogen atoms jumping from the first energy level
to the second energy level. Likewise, no light with an energy of
1.89 eV will make it through; those photons will be absorbed by
hydrogen atoms jumping from the second energy level to the third
energy level. The light that the hydrogen cloud absorbs shows up
as dips in the cloud's spectrum. If the cloud were too hot,
however, all its hydrogen