In 2022, scientists detected a peculiar signal emanating from the most powerful cosmic explosion ever recorded. Now, they have deciphered the source: matter and antimatter colliding and annihilating each other at a staggering 99.9% the speed of light. This extraordinary cosmic event, a gamma-ray burst (GRB), is a colossal explosion of gamma-ray light unleashed when a massive star collapses into a black hole. As the newly formed black hole devours surrounding matter, some of that matter is propelled in the opposite direction, forming powerful energy jets that pierce through the dying star’s outer layers, according to NASA. When these jets are directed towards Earth, space-based satellites and spacecraft are able to detect them.
The brightest gamma-ray burst on record, nicknamed the BOAT (Brightest Of All Time) and officially named GRB 221009A, was observed on October 9, 2022. Its intense gamma-ray emission overwhelmed detectors onboard spacecraft orbiting Earth, including NASA’s Fermi Gamma-ray Space Telescope. The detectors temporarily shut down during the peak of the explosion. After about five minutes, the burst subsided, and the detectors resumed operation. However, they detected an unusual energy peak, lasting approximately 40 seconds, around 12 million electron volts, a significant energy level compared to visible light, which has an energy of around 2 to 3 electron volts.
Lead researcher Maria Edvige Ravasio, an astrophysicist at Radboud University and the Brera Observatory, expressed her astonishment at the signal: “When I first saw that signal, it gave me goosebumps.” While scientists have studied GRBs for half a century, this is the first time they have detected a signal like this with high certainty.
The unusual energy peak, researchers believe, is evidence of electrons and their antimatter counterparts, positrons, colliding and annihilating each other. Typically, this annihilation releases energy of around half a million electron volts. However, the observed energy of 12 million electron volts can be explained by the jets’ near-light-speed travel towards Earth, which compresses the waves, leading to a “blueshift” that pushes the waves towards higher energy levels in the “bluer” end of the electromagnetic spectrum.
Om Sharan Salafia, an astrophysicist at the National Institute for Astrophysics (INAF)-Brera Observatory, emphasized the statistical significance of the findings: “The odds this feature is just a noise fluctuation are less than one chance in half a billion.” This discovery sheds light on the tumultuous environment within these jets, providing valuable information about processes that remain poorly understood despite decades of study. The research was published in the journal Science on July 25th.
