Some Consequences of the Baryonic Dark Matter Population
  Microlensed double-image quasars have sent a consistent message that the baryonic dark matter consists of a population of free-roaming planet mass objects, as summarized previously. These were previously predicted to have formed at the time of recombination, 300,000 years after the Big Bang, whence they collapsed on a Kelvin Helmholz time scale. Today they are glimpsed as the cometary knots in planetary nebulae. But they probably also nucleate the mysterious Lyman-alpha clouds and cause a reduction in the transparency of the universe to distant quasars and supernovae. 
Rudolph E. Schild