  The reliable theory of the evolution of heavy stars predicts the existence of
a type of neutron stars which accrete a cloud of dirty hydrogen (accretors).
Although they are very small (some hundreds of kilometres), the accretors
should be easily observable because the accretion raises the surface
temperature over 1 000 000 K, but they are never detected. The reason of this
failure is a misunderstanding of the spectroscopy of hydrogen crossed by a
powerful beam of short wavelengths light. Except very close to the surface,
hydrogen is mostly heated by a Lyman absorption improved by a parametric
frequency shift due to excited atomic hydrogen, so that this absorption
stabilises the temperature between the limits of ionisation and dimerisation. A
powerful radio emission may produce an extra ionisation where the pressure is
convenient. The combination of Lyman absorptions and redshifts produces an
instability which chains Lyman absorption patterns : when a redshifted Lyman
absorbed line coincides with a Lyman line, all absorption lines of the gas are
written into the spectrum. Thus all characteristics of the complex spectrum of
a quasar are generated, so that observed accretors are named quasars, and the
origin of the intrinsic redshifts is found. The lack of redshifts of the
variations of luminosity of stars and quasars shows that the "cosmological
redshifts" result from the parametric frequency shift, so that the universe
does not expand.
