The cosmic explosions so powerful they were discovered by accident
In the 1960s, US military satellites were hunting for illegal nuclear tests. Instead, they stumbled upon the most energetic events in the known universe: gamma-ray bursts. These brief, intense flashes of high-energy light can outshine our Sun by a quintillion times.
Gamma-ray bursts (GRBs) are brief, intense outbursts of the highest-energy light. Astronomers categorize them into two distinct classes based on their duration. Short bursts last less than two seconds—often averaging just 0.3 seconds—and are typically triggered by the collision of compact objects, such as two neutron stars or a neutron star merging with a black hole. Long bursts last two seconds or more, often spanning several minutes, and are linked to the catastrophic deaths of massive stars.
The underlying mechanism for both types involves the birth of a black hole. As the core of a massive star collapses or compact objects merge, a newborn black hole fires narrow, high-speed jets of particles in opposite directions. When these jets encounter surrounding gas and dust, they emit gamma rays. As the jets expand and sweep up material, they create an 'afterglow' that can be tracked across the electromagnetic spectrum, from X-rays to radio waves, for days or even years.
While much is understood, significant mysteries remain. For instance, the 2020 detection of GRB 200826A by the Fermi Telescope challenged existing classifications because its one-second duration sat on the boundary of the two classes. Furthermore, while short bursts are sometimes followed by kilonovae—events that produce heavy elements like gold and platinum—the full complexity of these cosmic engines continues to evolve as new satellite data arrives.
Source: NASA Explains Gamma-ray Bursts
