In quasar spectra, the region next to the Gunn-Peterson trough contains a series of lines caused by this transition, known as its namesake forest.
Charles Steidel discovered a pair of emitters of this phenomenon, one of which was dubbed the "Newfound Blob". A cloud within Cetus called "Himiko" is noted for emitting this line strongly, and a type of galaxy named for this distant phenomenon are used to study dark matter distribution and show this phenomenon due to bursts of star formation. It has a wavelength of around 1215 angstroms, which is equal to 4 over three times the Rydberg constant. In quasar spectra, the region next to the Gunn-Peterson trough contains a series of lines caused by this transition, known as its namesake forest. For 10 points, name this spectral line that is caused by the electronic transition from the n = 2 to n = 1 state in a hydrogen atom.
Charles Steidel discovered a pair of emitters of this phenomenon, one of which was dubbed the "Newfound Blob".
Lyman-alpha line [prompt on ultraviolet or UV]