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Astronomy

Gamma-ray bursts as probes of the early universe

Quick fact

The most distant known gamma-ray burst, GRB 090423, exploded just 630 million years after the Big Bang, when the universe was only about 4.5% of its current age.

Why this is interesting

Imagine witnessing an explosion so bright that it outshines every star in the universe combined—but only for a few seconds. How can such a fleeting flash from billions of light-years away tell us about the universe's very first stars?