NASA's Fermi Telescope Discovers Unprecedented Emission Line in Record-Breaking Gamma-Ray Burst

A significant discovery has been made by astronomers analyzing data from NASA's Fermi Gamma-ray Space Telescope related to the brightest gamma-ray burst (GRB) ever observed. Graced with the acronym, BOAT - the "brightest-of-all-time" gamma-ray burst – the event, which happened on October 9, 2022, is the current record holder for such phenomena. It has yielded unprecedented insights that could greatly enhance our understanding of the universe.

The international science team led by Maria Edvige Ravasio has reported an unusual energy peak in the data from Fermi's Gamma-ray Burst Monitor. Occurring minutes after the onset of the BOAT and persisting for at least 40 seconds, this peak represents the first high-confidence emission line seen in 50 years of GRB investigations. Her initial reaction to the signal, Ravasio described, was visceral – it sent shivers down her spine.

The significance of this anomaly is immense, with Om Sharan Salafia, one of the coauthors, emphasizing the statistical improbility of this feature being a mere noise fluctuation. Such an occurrence, he notes, is less likely than one in half a billion, a testament to the novelty of the finding reported in the July 26 edition of the journal Science.

GRBs are extraordinarily energetic explosions, often heralding the death throes of massive stars that end their lives in a final collapse and the subsequent formation of a rapidly spinning black hole. As the core falls inward, jets of particles shoot outwards at almost the speed of light, sometimes aligning with the Earth and allowing detection. The BOAT saturated gamma-ray detectors on Fermi and others in orbit, hinting at its unparalleled brightness, which reconstruction suggests might be the most intense burst seen on Earth in 10,000 years.

The distinction of this event is not just its intensity but the spectral feature it exhibited. The emission line, which appeared at an energy peak of about 12 MeV – millions of times more energetic than visible light – could potentially be attributed to the annihilation of electron-positron pairs in high-speed collision. The jet's direction facing Earth suggests a blueshift in the emission, with the annihilating particles thought to be moving at approximately 99.9% the speed of light.

This assumption, posited by coauthor Gor Oganesyan, if proven correct, could influence our current conception of cosmic jet mechanisms and the physics of such colossal explosions. Elizabeth Hays, the Fermi project scientist, contemplates that these findings serve as crucial pointers that can propel further in-depth investigation into these extreme cosmic conditions.

The Fermi Gamma-ray Space Telescope represents a collaboration between astrophysics and particle physics communities, managed by NASA's Goddard Space Flight Center. Development contributions hail from a global consortium including academic institutions and various countries such as France, Germany, Italy, Japan, Sweden, and the U.S.