Astronomers detect first ‘heartbeat’ of newborn star hidden in powerful cosmic explosion
Gamma-ray bursts are the brightest explosions in the universe, briefly eclipsing entire galaxies in a violent flash of high-energy radiation. These astronomical detonations – excuse the pun – release more energy in seconds than our sun will produce in its entire ten-billion-year lifespan, sending jets of gamma rays across space. Despite their incredible luminosity, gamma-ray bursts are ephemeral events, lasting from a few milliseconds to several minutes before disappearing.
On March 7, 2023, satellites detected one of these gamma-ray bursts, this one designated GRB 230307A. It is the second brightest burst ever recorded and results from the collision and merger of two compact stars, probably neutron stars, located in a distant galaxy. What made this event particularly curious was its unusually long duration of one minute, when theory predicted it should last less than two seconds for this type of merger event.
“This event gave us a rare opportunity: by discovering its hidden ‘heartbeat,’ we can finally say with certainty that some GRBs are not powered by black holes, but by newborn magnetars.”
Professor Bing Zhang, full professor in the Department of Physics at HKU and co-corresponding 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 investigate the event further. They combed through more than 600,000 data sets collected by China’s GECAM and NASA’s Fermi satellites, looking for hidden patterns in the explosion. What they found was a repeating signal that maintained a very constant rhythm over time, revealing that the star was rotating at 909 times per second. This rapid pulsation represents the first direct detection of a periodic signal from a millisecond magnetar inside a gamma-ray burst.
The surprise was to understand why the signal was so brief. The team hypothesizes that the rapid rotation of the magnetar imprints a periodic signal on the gamma-ray jet through its magnetic field, but because the jet evolves rapidly, this heartbeat only becomes visible when the emission briefly becomes asymmetric. For only 160 milliseconds, the periodic pulse was detectable before the symmetry of the jet concealed it again.
This discovery transforms our understanding of the universe’s most extreme explosions and shows that newly born magnetars can survive mergers of compact stars. The research opens fascinating new avenues in astronomy, linking gamma rays, gravitational waves and the physics of compact stars under the most extreme conditions imaginable.
THE original version of this article was published on The universe today.
