Message #184854

[Uriel]

Cosmic dark ages
After the Big Bang, the universe had cool rapidly as it expanded. About 400,000 years later, free electrons and protons (negative and positive charges, respectively) combined to form neutral atoms, leaving the universe awash in a background radiation that we currently can detect in the microwave part of the electromagnetic spectrum (the so-called Cosmic Microwave Background).

The universe stayed in this neutral stage until the first stars and galaxies light it up. The photons from these stars knocked electrons free from the atoms, "re-ionizing" the universe. But detecting the most distant galaxies and quasars from this period is difficult, and so astronomers are hoping that distant gamma-ray bursts such as GRB 090423 will give them information about this re-ionization period.

It will likely take many more gamma-ray bursts to say anything definitive about this cosmic dark age though.