A gamma-ray burst is a brief but extremely powerful flash of light, born from the merger of neutron stars or the collapse of a massive star. Inside such a flash, plasma flows race at enormous speeds and collide with each other. The shock wave from the collision heats the matter, and it begins to glow: this is how the radiation we detect on Earth is born.
For a long time, scientists couldn't precisely calculate how light is generated inside a gamma-ray burst. The problem is that this radiation itself pushes on the plasma and alters its motion, like a flashlight pushing against fog. The authors of the new study built the first computer model that accounts for this mutual influence in full detail. They traced the path of the shock waves from their birth to the light escaping outward.
The result was surprising: the reverse shock (the one moving backward through the incoming flow) continues to 'glow' even where the plasma is already nearly transparent to radiation. Previously, it was thought that in such regions, light no longer affects matter. Now it's clear that the influence persists longer than expected. Light is scattered not at a single sharp surface, but over a wide range of distances, like fog scattering headlights not at one point, but throughout its entire thickness.
As a result, the radiation spectrum resembles real gamma-ray bursts: many low-energy photons and fewer high-energy ones. This means the model accurately describes the physics inside the burst. Understanding these processes will help us better read signals from distant cosmic catastrophes.
In one second, a gamma-ray burst can release more energy than the Sun will emit over its entire lifetime.