Astronomers detect most powerful explosions since Big Bang
ENTs are as devastating as they are rare. They only occur when a massive star at least three times heavier than the sun drifts too close to a supermassive black hole. The colliding forces subsequently obliterate the star, sending out plumes of energy across huge swaths of space. Similar events known as tidal disruption events (TDEs) are known to occur on a (comparatively) smaller scale, and have been documented for over a decade. But ENTs are something else entirely.
'ENTs are different beasts,' study lead author and astronomer Jason Hinkle explained in an accompanying statement. '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.'
Hinkle was first tipped off to ENTs while looking into transients—longlasting flares that spew energy from a galaxy's center. Two particularly strange examples captured by the European Space Agency's Gaia mission caught his eye. The pair of events brightened over a much longer timeframe than previously documented transients, but lacked some of their usual characteristics.
'Gaia doesn't tell you what a transient is, just that something changed in brightness,' 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 soon reached out to observatory teams around the world for what would become a multiyear project to understand these anomalies. In the process, a third suspect was detected by the Zwicky Transient Facility at the Palomar Observatory in San Diego. After months of analysis, Hinkle and collaborators realized they were witnessing something unprecedented.
The ENTs analyzed by astronomers displayed smoother, longer lasting flares that pointed towards something very particular—a supermassive black hole accreting a giant, wayward star.
This contrasts with a more standard black hole that typically acquires its material and energy unpredictably, resulting in irregular brightness fluctuations.
The energy and luminosity of an ENT boggles the mind. The most powerful ENT documented in Hinkle's study, Gaia18cdj, generated 25 times more energy than the most powerful known supernovae. For reference, a standard supernova puts out as much energy in a single year as the sun does across its entire 10 billion year lifespan. Gaia18cdj, meanwhile, manages to give off 100 suns' worth of energy over just 12 months.
The implications of ENTs and their massive energy surges go far beyond their impressive energy outputs. Astronomers believe they contribute to some of the most pivotal events in the cosmos.
'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,' said Hinkle.
From here on Earth, ENTs can also help researchers as they continue studying massive, distant black holes.
'Because they're so bright, we can see them across vast cosmic distances—and in astronomy, looking far away means looking back in time,' explained study co-author and astronomer Benjamin Shappee. 'By observing these prolonged flares, we gain insights into black hole growth when the universe was half its current age… forming stars and feeding their supermassive black holes 10 times more vigorously than they do today.'
There's a catch for astronomers, however. While supernovae are relatively well-documented, ENTs are estimated to occur at least 10 million times less often. This means that further study requires consistent monitoring of the cosmos backed by the support of international governments, astronomical associations, and the public.
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