Collectively the Lyman-alpha clouds
impose a complex of absorption lines known as the "Lyman-alpha forest" on the visible light spectrum of the distant quasar .
Models of gravitational clustering in the early universe predict different distributions of these Lyman-alpha clouds
depending on how much mass is assigned to the neutrinos that were spawned from the Big Bang.
He and his colleagues report in the April 1 Astrophysical Journal that some Lyman-alpha clouds
, rather than residing between galaxies, actually constitute vast halos around galaxies.
Totally unexpected was the early profusion of what are now called Lyman-alpha clouds
- tenuous, highly ionized clouds poor in heavy elements that once filled the spaces between major galaxies.
Galaxy counterparts for more distant Lyman-alpha clouds
remain to be identified - if indeed they exist!