Twenty-eight seconds: that's how long it took for an automated camera to lock onto a flash in a constellation whose light had traveled for more than nine billion years. The telescope at the Ondřejov Observatory in the Czech Republic worked like a fire alarm: as soon as a satellite detected a gamma-ray burst, a robot swung the tube around and started photographing the sky every few seconds. This allowed us to see not just a distant explosion, but its first minutes — the brightest and most mysterious ones.

At first, the light flared up like a light bulb switched to full power. Then, after a minute and a half, something strange happened: the brightness jumped again, leveled off on a plateau, and then dropped sharply — faster than a typical afterglow should. This pattern doesn't match a shock wave accelerating particles to enormous speeds. Instead, in the cloud of hot gas, electrons first moved chaotically, like a crowd at a train station, and then their energy was released as radiation — leaving a trace of that cooling in visible light.

The model showed that almost all the explosion's energy went not into a shock wave but into heating the electrons themselves. They turned out to be as hot as sparks from a fire, and as they cooled, they illuminated the gas cloud from within. This is the first time such a thermal signature has been seen in a gamma-ray burst afterglow. It had been predicted by calculations before, but never caught live.

Now the picture of the first minutes after the explosion is clearer. As hot electrons cool, they paint their pattern in the light, and that pattern can be read like an entry in a ship's log. A telescope that arrived in half a minute has opened a new page in the history of cosmic catastrophes.