What phenomenon allows a Gamma-Ray Burst (GRB) to briefly outshine the entire observable universe in its specific wavelength?

Answer

Gamma rays are the most energetic photons in existence

Gamma rays carry far more power than other forms of electromagnetic radiation, allowing these catastrophic events, like GRBs, to temporarily dominate the energy output in that specific wavelength across the observable universe.

What phenomenon allows a Gamma-Ray Burst (GRB) to briefly outshine the entire observable universe in its specific wavelength?
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