USAAAO — 2026 First Round

The Balmer-α, H-I, and Lyman-α lines are important spectral lines in astronomy, all from hydrogen. The Balmer-α line occurs when an electron in a hydrogen atom goes from the n = 3 state to n = 2. The H-I line occurs from an electron in the 1s shell of a hydrogen atom undergoing a spin-flip transition between two hyperfine levels. The Lyman-α line is the emission line that occurs when an electron in a hydrogen atom goes from n = 2 to n = 1. Order these lines from the shortest to longest wavelength.