High-energy explosions in the sky are often attributed to gamma-ray bursts. We now know that these explosions result from the merger of two neutron stars, or the collapse of a massive star. In these scenarios, a new black hole forms, emitting jets that travel at nearly the speed of light. As these jets travel towards Earth, a relativistic effect called the Doppler effect allows us to observe them from great distances, sometimes billions of light years away. Thousands of such gamma-ray bursts have been detected in the past decade.
The Einstein Probe, an X-ray space telescope developed by the Chinese Academy of Sciences (CAS) in collaboration with the European Space Agency (ESA) and the Max Planck Institute for Extraterrestrial Physics, has been scanning the skies for high-energy bursts since its launch in 2024, and in April observed an unusual event named EP240408A. Currently, an international team of astronomers, including Dheeraj Pasham of MIT, Igor Andreoni of the University of North Carolina at Chapel Hill, and Brendan O’Connor of Carnegie Mellon University, are investigating the burst using a range of ground- and space-based telescopes, including NuSTAR, Swift, Gemini, Keck, DECam, VLA, ATCA, and NICER, all developed in collaboration with MIT.
An open-access report on the findings, published January 27 in the Astrophysical Journal Letters , notes that the burst’s characteristics don’t match those of a traditional gamma-ray burst. Instead, it may represent a rare and new type of powerful cosmic explosion: a tidal disruption event that occurs when a supermassive black hole rips a star apart.
“NICER’s ability to travel to almost any part of the sky and monitor for weeks at a time will make it crucial to understanding these unusual cosmic outbursts,” said Pasham, a research scientist at MIT’s Kavli Institute for Astrophysics and Space Sciences.
While it’s possible that jets could cause tidal disruption events, the lack of radio emissions from the jets is puzzling, the researchers say. O’Connor speculates, “EP240408a meets some but not all of the criteria for different types of events. In particular, its short duration and high brightness are hard to explain in other scenarios. Or, perhaps we’re looking at something entirely new.”
According to Pasham, the Einstein Probe has only just begun to scratch the surface of what’s possible: “I’m very excited to pursue the next unusual explosion with the Einstein Probe,” he said, echoing astronomers around the world who are excited about the possibility of finding even more unusual explosions in the farthest reaches of the universe.
