Gamma-ray bursts are the brightest explosions in the universe, briefly overwhelming entire galaxies in a violent flash of high-energy radiation. These astronomical explosions—pardon the pun—release more energy in a few seconds than our Sun will produce in its 10 billion-year lifetime, sending jets of gamma rays racing across space. Despite their amazing brightness, gamma-ray bursts are transient events, lasting from milliseconds to several minutes before fading.
On March 7, 2023, satellites detected one of these gamma-ray bursts, named GRB 230307A. This was the second brightest explosion ever recorded, and it resulted from the collision and merger of two merged stars, likely neutron stars, located in a distant galaxy. What made this event particularly intriguing was its unusually long duration, one minute, when theory predicted it should last less than two seconds for this type of fusion event.
“This event has given us a rare opportunity that, by revealing hidden ‘heartbeats’, we can finally say with confidence that some GRBs derive their energy not from black holes, but from newborn magnetars.”
Professor Ping Zhang, Chair Professor of the Department of Physics at the University of Hong Kong and co-author of the study.
An international team led by researchers from the University of Hong Kong, Nanjing University, and the Chinese Academy of Sciences decided to delve into this event. They looked at more than 600,000 datasets collected by China’s GECAM satellites and NASA’s Fermi satellite search for hidden patterns within the explosion. What they found was a recurring signal that maintained a very constant rhythm over time, revealing that the star was rotating at a rate of 909 times per second. This fast pulse represents the first direct detection of a millisecond periodic signal from a magnetar within a gamma-ray burst.
The surprise was understanding why the signal was so short. The team hypothesizes that the magnetar’s rapid rotation imprints a periodic signal on the gamma-ray jet through its magnetic field, but because the jet develops rapidly, these heartbeats only become visible when the emission briefly becomes asymmetric. For only 160 ms, the periodic pulse was detectable before the jet’s symmetry masked it again.
This discovery changes our understanding of the most extreme explosions in the universe and shows that newborn magnetars can survive the merger of compact stars. This research opens fascinating new horizons in astronomy, linking gamma rays, gravitational waves and the physics of compact stars under the most extreme conditions imaginable.
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