University of Hawaiʻi astronomers discover biggest explosion since the Big Bang

A team at the University of Hawaiʻi’s Institute for Astronomy has uncovered a dazzling new kind of cosmic explosion, more energetic than anything seen before, according to a news release from the university.

The team named these rare events “extreme nuclear transients,” which occur when massive stars, which are at least three times the mass of the Sun, are shredded by supermassive black holes. 

The team’s findings were recently published in Science Advances.

“We’ve observed stars getting ripped apart as tidal disruption events for over a decade, but these ENTs are different beasts, reaching brightnesses nearly 10 times greater than what we typically see,” said Jason Hinkle, who led the study as the final piece of his doctoral research at the Institute for Astronomy.

He said the extreme nuclear transients are 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.

These extreme nuclear transients are millions of times rarer than supernovae. But their extreme brightness means they can be seen even in extremely distant galaxies, giving scientists a new way to study black holes in the early universe, the news release said.

One of the ENTs studied in this work, named Gaia18cdj, released 25 times more energy than the most powerful supernova on record. In just one year, it radiated energy equal to the lifetime output of 100 Suns. Most supernovae, in comparison, produce only one Sun’s lifetime output over a similar timescale.

Hinkle first spotted the strange flares while combing through publicly available data from the Gaia space telescope. Unlike more common cosmic explosions that fade over several weeks, extreme nuclear transients glow steadily for years.

“Gaia observations don’t tell you what a transient is, just that something changed in how bright it appears to us,” Hinkle said. “But when I saw these smooth, long-lived flares from the centers of distant galaxies, I knew we were looking at something unusual.”

Hinkle used years of observations from UH’s Asteroid Terrestrial-impact Last Alert System with telescopes on Haleakalā on Maui and Mauna Loa on the Big Island, as well as the W. M. Keck Observatory on Maunakea on the Big Island, and other telescopes on and orbiting the Earth to characterize these events.

Researchers confirmed these weren’t supernovae or normal black hole activity. Instead, ENTs appear to be caused by a smoother, more drawn-out process, stars multiple times as massive as our Sun being slowly consumed by black holes.

“ENTs provide a valuable new tool for studying massive black holes in distant galaxies,” said Benjamin Shappee, an associate professor at the Institute for Astronomy who co-authored the study. “Because they’re so bright, we can see them across vast cosmic distances — and in astronomy, looking far away means looking back in time.

“By observing these prolonged flares, we gain insights into black hole growth when the universe was half its current age and galaxies were busy places — forming stars and feeding their supermassive black holes 10 times more vigorously than they do today.”

Astronomers hope to spot many more ENTs, with each offering a glimpse into the powerful forces shaping galaxies across cosmic time. Future observatories such as the Vera C. Rubin Observatory and NASA’s Roman Space Telescope could uncover many more of these spectacular events, revolutionizing our understanding of black hole activity in the distant, early universe.

“These ENTs don’t just mark the dramatic end of a massive star’s life,” Hinkle said. “They illuminate the processes responsible for growing the largest black holes in the universe.”