Astronomers have revealed the detection of extreme nuclear transients (ENT), a newly identified class of cosmic events that represent the most energetic explosions ever observed.
Researchers at the University of Hawaii’s Institute for Astronomy (IfA) made the explosive discovery, witnessing enormous stars, each with masses at least three times that of the Sun, straying too close to the destructive pull of supermassive black holes. The result is an immense release of energy, visible across vast stretches of space due to its extraordinary brightness.
Extreme Nuclear Transients
“We’ve observed stars getting ripped apart as tidal disruption events for over a decade, but these ENTs are different beasts, reaching brightnesses nearly ten times more than what we typically see,” said lead author Jason Hinkle. “Not only are ENTs far brighter than normal tidal disruption events, but they remain luminous for years, far surpassing the energy output of even the brightest known supernova explosions.”
The luminosity and energy of these extreme nuclear transients surpass anything previously recorded. One such event, Gaia18cdj, was the most powerful of the group, releasing 25 times more energy than the strongest supernovae on record. For perspective, an average supernova releases as much energy in a year as our Sun will emit over its entire 10-billion-year lifetime. A typical ENT, however, releases 100 times more energy than that annually.
Discovering ENTs
Hinkle’s research began with a detailed analysis of public transient surveys, searching for long-lived flares emerging from galactic centers. Two flares stood out while examining data from the European Space Agency’s Gaia mission. These anomalies grew brighter over a far more extended period than most known transients and exhibited behaviors that didn’t match standard transient events.
“Gaia doesn’t tell you what a transient is, just that something changed in brightness,” said Hinkle. “But when I saw these smooth, long-lived flares from the centers of distant galaxies, I knew we were looking at something unusual.”
Pursuing the Unusual Observations
Years of research followed, as the flares evolved over extended timescales. Additional electromagnetic data from UH’s Asteroid Terrestrial-impact Last Alert System, the W. M. Keck Observatory, and other international telescopes helped fill in the picture. The most recent ENT, discovered by the Zwicky Transient Facility and confirmed by two separate teams, added a third example to the growing list.
Hinkle’s team determined that these events could not be supernovae due to the immense energy involved. Instead, they appear to represent an entirely new class of stellar explosion. While black hole accretion remains the leading explanation, ENTs exhibit smooth, prolonged increases in brightness, unlike typical black hole accretion events, which tend to fluctuate unpredictably.
“ENTs provide a valuable new tool for studying massive black holes in distant galaxies. Because they’re so bright, we can see them across vast cosmic distances—and in astronomy, looking far away means looking back in time,” said co-author Benjamin Shappee, Associate Professor at IfA. “By observing these prolonged flares, we gain insights into black hole growth when the universe was half its current age—when galaxies were happening places—forming stars and feeding their supermassive black holes 10 times more vigorously than they do today.”
Continuing the Search
Astronomers can only hope to uncover more extreme nuclear transients by constantly monitoring the skies. Hinkle’s team estimates that ENTs are 10 million times rarer than supernovae. Two upcoming instruments, the Vera C. Rubin Observatory and NASA’s Roman Space Telescope, are expected to provide powerful new tools for locating these rare, massive explosions.
“These ENTs don’t just mark the dramatic end of a massive star’s life. They illuminate the processes responsible for growing the largest black holes in the universe,” concluded Hinkle.
The paper “The Most Energetic Transients: Tidal Disruptions of High-Mass Stars” appeared on June 04, 2025, in Science Advances.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.