The spectrum of hydrogen is particularly important in astronomy because most of the Universe is made of hydrogen. Emission or absorption processes in hydrogen occur in multiple series, which are sequences of lines corresponding to atomic transitions, each ending or beginning with the same energy level in hydrogen. Thus, for example, the Balmer Series involves transitions starting (for absorption) or ending (for emission) with the first excited state of hydrogen, while the Lyman Series involves transitions that start or end with the ground state of hydrogen.  The image below illustrates these and other transitions between energy levels.  The ground state is labeled as n=1.

Because of the wide range of energy gaps in hydrogen's atomic structure, the Balmer Series is in the visible spectrum and the Lyman Series is in the the UV. The following image illustrates some of the transitions in the Balmer series. These are the true colors of the emitted lines which you will soon see for yourself.

The Balmer spectrum of hydrogen The Balmer lines are designated by H with a greek subscript in order of decreasing wavelength. Thus the longest wavelength Balmer transition is designated H with a subscript alpha, the second longest H with a subscript beta, and so on.