2024-08-08 06:00:15
Studying data from NASA’s Fermi gamma-ray space telescope, researchers observed a unique energy spike after the brightest gamma-ray burst ever seen, suggesting the annihilation of electrons and positrons.
In October 2022, astronomers were surprised by a gamma-ray burst (GRB) called BOAT (brightest-of-all-time). A team of scientists discovered that the Fermi telescope had detected a spectral feature that had never been seen before. Maria Edvige Ravasio, from theuniversité Radboud and the Brera Observatory, underlines the importance of this discovery, the first in 50 years of studying GRBs.
Interactions between matter and light can reveal valuable information. At high energies, they show peculiar processes, such as the annihilation of particles and antiparticles that produce gamma rays. Om Sharan Salafia, co-author of the study, believes that the probability that this feature is a statistical fluctuation is very low.
GRBs are the most powerful explosions in the universe, emitting large quantities of gamma rays. They occur when the core of a massive star collapses into a black hole, generating jets of particles traveling almost at the speed of light. The BOAT, identified as GRB 221009A, is probably the brightest explosion of the past 10,000 years.
Five minutes after the BOAT detection, an emission line appeared, peaking at 12 MeV. The team believes it results from the annihilation of electrons and positrons. Gor Oganesyan of the Gran Sasso Science Institute explains that this emission, observed in the jet, is strongly blueshifted.
A jet of particles moving nearly at the speed of light emerges from a massive star in this illustration. The star’s core has collapsed into a black hole, redirecting some of the material into opposing jets. We see a gamma-ray burst when one of these jets points toward Earth.
Crédit: NASA’s Goddard Space Flight Center Conceptual Image Lab
If this interpretation is correct, the annihilated particles would have been traveling at about 99.9 percent the speed of light. Fermi project scientist Elizabeth Hays points out that this discovery is a key to exploring this extreme environment more deeply. The Fermi telescope is the result of an international collaboration, including significant contributions from France, Germany, Italy, Japan, Sweden and the United States.
Matter/antimatter annihilation
Matter/antimatter annihilation is a physical phenomenon where a matter particle meets its antiparticule corresponding. During this encounter, the two particles destroy each other, or annihilate each other, releasing a large amount of energy in the form of gamma rays.
For example, when an electron meets a positron (its antiparticle), they annihilate to produce two gamma photons. This process is particularly important in astrophysics and in particle physics because it allows us to better understand the fundamental interactions in the universe, the properties of particles, and extreme energetic phenomena such as gamma ray bursts.
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