S. Ansoldi

In a courtroom, there isn't always a video recording of the crime. Sometimes the verdict is based on witness testimony: what happened before, what happened after. That's exactly how physicists treated the signal GW250114, detected on January 14, 2025.

Seven billion years ago, a black hole at the center of a galaxy unleashed a gamma-ray flare — the most energetic form of light — with staggering power. Its light, after crossing cosmic distances, reached the MAGIC telescopes in December 2017.

After a supernova explosion, a neutron star neutron star remains: a city-sized ball of unimaginably dense matter, spinning hundreds of times per second. Any tiny bump on its surface would make it wobble like an off-balance spinning top, humming faintly through the fabric of space.