Cosmic Monsters: Astronomers Spot Most Powerful Explosions Yet

In what researchers are calling the biggest cosmic bang since the Big Bang itself, astronomers from the University of Hawaiʻi’s Institute for Astronomy (IfA) have uncovered a new and astonishing class of cosmic explosions—ones so powerful they outshine anything we’ve ever witnessed in the known universe. These extreme events, dubbed “extreme nuclear transients” (ENTs), are rewriting what we thought we knew about the death of stars and the monstrous appetite of supermassive black holes.

The discovery comes after over a decade of scientists observing tidal disruption events—those violent occasions when stars venture too close to a galaxy’s central supermassive black hole and are torn to shreds. But these newly detected ENTs are on a whole different level, both in brilliance and longevity.

“We’ve seen stars get ripped apart before, but these are in a league of their own,” said Jason Hinkle, the lead author of the study and now a Ph.D. graduate from IfA. “These ENTs shine up to ten times brighter than typical tidal disruption events, and their light lingers for years — something unheard of even with the most energetic supernovae.”

To grasp the scale of these explosions: a typical supernova emits in one year the same amount of energy our Sun will radiate over its entire 10-billion-year lifetime. ENTs? They release the energy equivalent of 100 Suns in a single year. One record-breaking event, named Gaia18cdj, spewed out 25 times more energy than the most powerful known supernova.

Hunting Giants in the Darkness

The story began when Hinkle took on the painstaking task of combing through public transient surveys, looking for long-lasting flares from the hearts of distant galaxies. The European Space Agency’s Gaia mission flagged two mysterious signals, but without specifying what they were.

“Gaia tells you something’s changed in brightness, but not what or why,” explained Hinkle. “When I saw these smooth, unusually long-lived flares coming from galactic centers, I realized this was something completely different.”

That triggered a multi-year, international observation campaign, involving telescopes like Hawaiʻi’s own W. M. Keck Observatory, the Asteroid Terrestrial-impact Last Alert System (ATLAS), and other powerful eyes on the sky worldwide. Because ENTs evolve over several years — a cosmic eternity in transient terms — it required both scientific patience and relentless follow-ups.

The efforts paid off. A third event, strikingly similar to the first two, was later detected by the Zwicky Transient Facility and independently reported by two other teams, solidifying the idea that ENTs represent a new, distinct class of extreme cosmic phenomena.

Not Your Typical Stellar Death

So what exactly causes these ultra-bright, long-lasting explosions? It turns out, not supernovae. The energy output of ENTs is far too massive for even the most dramatic stellar explosions. Instead, the culprit appears to be the gradual, steady consumption of a star by a supermassive black hole.

But ENTs don’t behave like normal black hole feeding events either, which tend to be erratic and unpredictable. These flares are smooth, long, and bright — evidence of a different process at play. It’s thought that as a massive star gets shredded, its matter spirals into the black hole in a slow, consistent stream, generating an enormous, sustained release of energy.

A New Window Into Ancient Cosmos

Why does this matter? According to Benjamin Shappee, IfA associate professor and co-author of the study, ENTs offer a rare tool for studying how black holes grew during the universe’s younger years.

“Because these flares are so bright, we can spot them from extreme distances. And in astronomy, distance equals time — the farther we look, the further back in history we’re seeing,” Shappee said. This means ENTs can give us a front-row seat to the era when galaxies were teeming with new stars and ravenous black holes gobbled up surrounding material at rates far higher than today.

A Cosmic Rarity — and What’s Next

ENTs are exceptionally rare, occurring at least 10 million times less often than supernovae. This makes them notoriously hard to catch without constant sky surveys. But future observatories like the Vera C. Rubin Observatory and NASA’s Roman Space Telescope, set to launch later this decade, promise to dramatically boost our chances of discovering more.

“These aren’t just spectacular explosions marking the death of massive stars,” said Hinkle. “They’re crucial clues about how the universe’s biggest black holes grew to their monstrous sizes.”