  A number of years ago the estimates of astronomers and astrophysicists were
that the earliest galaxies took about 2.5 to 3 billion years to form, that is,
that they did not appear until 2.5 to 3 billion years after the Big Bang. Those
estimates were based on analysis of the processes involved in star formation
and in the aggregation and "clumping" of matter in the early universe.
  Since then improved equipment and techniques, e.g. Keck and Hubble telescopes
and gravitational lensing, have resulted in reports of observation of early
galaxies having stars that formed as early as 300 million years after the Big
Bang.
  Such new data has led to the abandonment of the several billion years
estimates of the time required for star and galaxy formation; however, an
alternative response to the data would be to re-examine the Hubble theory from
which the age of the universe and the distance to high redshift objects is
determined.

General Physics