There are two galaxies recently described in the astronomical literature, 53W091with a redshift of 1.55 which is an extremely red galaxy, meaning very old. Also 6C 0140+326 with a redshift of 4.41. The first galaxy has a derived age of 3.5 billion years, but at its distance implies a redshift for when it was first formed of about Z = 6. The second galaxy joins a growing list of other very young galaxies or galaxy fragments undergoing explosive star forming activity, that imply that galaxies were being born at redshifts near 6 or so. This means that the universe at this time contained more collapsed objects that the favored 'modified Cold Dark Matter' version of Big Bang cosmology can predict. These findings, however, can be readily accommodated by low-Omega, open Big Bang models where the clumping at these small scales isn't in accord with the predictions by simple 'inflationary' cosmology.
Just this week I read a preprint about a new young galaxy detected at a redshift of 5. Again, this is very exciting because the time when the youngest galaxies can form provides a very severe test of some of the versions of Big Bang cosmology that we are still trying to decide between.
Copyright 1997 Dr. Sten Odenwald
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