Black holes create the brightest stellar explosions ever recorded

Astronomers have recently identified the brightest, longest-lasting stellar explosions ever seen. These colossal flares, produced when heavyweight stars stray too close to gigantic black holes, outshine even the most powerful supernovae.

Experts at the University of Hawaiʻi’s Institute for Astronomy have named the phenomenon “extreme nuclear transients,” or ENTs, because they erupt from galactic centers where supermassive black holes reside.

Each flare occurs after a star at least three times heavier than the Sun is ripped apart by tidal forces. The shredded material spirals inward, releasing energy that can be detected across billions of light-years.

Brighter than anything seen before

“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 Jason Hinkle, who completed the analysis during his doctoral work.

“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,” he said.

The most radiant example, Gaia18cdj, unleashed twenty-five times the energy of the record-holding supernova. In practical terms, a single ENT can emit the light of one hundred Suns every year it endures.

Distinct family of cosmic cataclysms

Hinkle first spotted the oddities while combing through alerts from the European Space Agency’s Gaia mission. That survey flags any object whose brightness changes, but it does not explain why.

“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.”

Those hints set off a global follow-up campaign. Observations came from the University of Hawaiʻi’s Asteroid Terrestrial-impact Last Alert System, the W. M. Keck Observatory atop Maunakea, and telescopes on several continents.

Because each flare unfolds over years rather than weeks, patience proved essential. While the work progressed, a third event with nearly identical traits appeared in data from the Zwicky Transient Facility and was reported by two independent teams.

The match confirmed that the stellar explosions inducted from black holes form a distinct family of cosmic cataclysms.

Why black holes explode stars

Supernova explosions cannot account for the energies involved. Even the mightiest supernova releases only a fraction of an ENT’s light.

Ordinary black hole feeding episodes also look different, flashing on and off in chaotic bursts. ENTs, by contrast, brighten smoothly and then fade at a slow, steady pace.

These features point to a specific process: a massive star’s gradual demolition and subsequent accretion onto a supermassive black hole.

Glimpses of ancient galaxies

Benjamin Shappee is the co-author of the analysis and an associate professor at the Institute for Astronomy.

“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 Shappee.

“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 ten times more vigorously than they do today.”

The rarity of these blasts adds to their value. An ENT is at least ten million times less common than a supernova, so spotting even a handful offers a unique probe of galactic cores during earlier cosmic eras.

Feeding habits of massive black holes

Future observatories promise to discover more such events. The Vera C. Rubin Observatory, scheduled to begin full operations soon, will scan the entire visible sky every few nights and alert astronomers to any fresh ENT candidates.

NASA’s Nancy Grace Roman Space Telescope, working from orbit, will supply prolonged infrared coverage, crucial for tracking the cool tails of these events.

Continuous monitoring will reveal how often massive stars wander into fatal orbits, and how quickly the resulting explosions feed the lurking black holes.

“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,” Hinkle said.

Each detection, therefore, serves two purposes: recording a stellar demise and exposing the feeding habits of black holes that weigh millions to billions of solar masses.

Watching cosmic chaos unfold

As survey cameras widen their reach, astronomers expect to uncover dozens – perhaps hundreds – of extreme nuclear transients throughout the observable universe.

Every new burst will stretch for years, giving scientists ample time to gather spectra, measure temperatures, and watch the gradual dimming.

Together, those observations will clarify how energy flows from infalling gas to outgoing radiation and how galactic nuclei evolve over cosmic time.

In the meantime, the three extreme nuclear transients already cataloged stand as the brightest, most enduring explosions on record.

The ENTs testify to forces powerful enough to dismantle giant stars, leading to explosions that black holes convert into blinding light. And they hint that the deepest reaches of space still hold bigger surprises than anything yet imagined.

The study is published in the journal Science Advances.

Image Credit: University of Hawaiʻi

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