On October 9, 2022, scientists observed the brightest gamma-ray burst (GRB) ever recorded, GRB 221009A. This one-in-a-lifetime event—nicknamed the “Brightest Of All Time” or BOAT—has generated international excitement among astronomers and astrophysicists. The nature of the burst’s intensity, though, was extraordinary. It saturated all of these observers’ observation instruments and ignited a fiery trail of follow-up studies across the globe.
Observatories based in space, including NASA’s Fermi and Swift satellites, were some of the first to pick up the signals from GRB 221009A. Once the detection was confirmed, the Large-Sized Telescope prototype—called LST-1—sprang into action. It started its first observations at the Cherenkov Telescope Array Observatory (CTAO-North) in La Palma, Spain, only 1.33 days after. LST-1 spent more than 20 days collecting critical data. This knowledge will immeasurably improve our knowledge of the mechanisms at play behind this most energetic of cosmic explosions.
The observations from the LST-1 corroborate the hypothesis that GRB 221009A was channeled by a complex and structured jet. This jet is made up of a thin, ultra-fast core cloaked by a thicker sheath of slower moving material. This framework provides an invaluable perspective on the processes that form jets in gamma-ray bursts. What was once a very mysterious and opaque topic is now getting easier to understand.
The LST-1 had difficulty making its observations due to bright moonlight conditions. This extreme illumination made it very difficult to collect data for Cherenkov telescopes that require sensitive cameras. Despite these difficulties, the LST Collaboration successfully deployed alert handlers that enabled automatic responses to transient events like GRB 221009A. By implementing this innovation, they were able to decrease follow-up reaction times and improve the quality of their observational data.
GRB 221009A is exceptional not just for its brightness but for its incredible energy output. In less than a minute, this cosmic event released more energy than the sun will emit in its entire lifetime. Yet, such a comparison serves to emphasize the importance of GRB 221009A as one of the greatest and most powerful phenomena ever observed in our universe.
The LST Collaboration recently released comprehensive results from their 2022 observations. These results underscore the remarkable potential of LST-1 in its commissioning phase at the Roque de los Muchachos Observatory. In this case, data collection uncovered a surplus of gamma rays associated with GRB 221009A. Consequently, scientists are now exploring the new findings’ implications for the theories of cosmic jet formation.