Lyman limitThe observed cutoff in the light from a cosmologically distant object, observed shortward of rest-wavelength 912A, and caused by photoelectric absorption in intervening hydrogen. The system responsible for the absorption is known as a Lyman limit system. The observed sharp drop in the rest-wavelength spectrum at 912A permits the discovery of high-redshift Lyman break galaxies, where this region of the spectrum is redshifted into the optical waveband.
Lyman limit[′lī·mən ‚lim·ət]
The lower limit of wavelengths of spectral lines in the Lyman series (912 angstrom units), or the corresponding upper limit in frequency, energy of quanta, or wave number (equal to the Rydberg constant for hydrogen).