Lyman Alpha is a specific wavelength of ultraviolet light emitted by hydrogen atoms. It occurs when an electron in a hydrogen atom transitions from the second energy level to the first, releasing energy in the form of a photon. This photon has a wavelength of about 121.6 nanometers, which is part of the electromagnetic spectrum. Astronomers often use Lyman Alpha emissions to study distant galaxies and interstellar gas. By observing these emissions, scientists can gain insights into the composition, temperature, and density of cosmic materials, helping to understand the evolution of the universe.