Astronomers have captured the biggest cosmic explosion ever detected. About 100 times bigger than the solar system and two trillion times brighter than the Sun at its peak, the mysterious miasma has remained visible for three years.
The universe is full of extreme events – stars go supernova with some regularity, black holes swallow objects with powerful burps, and cosmic collisions give off so much energy they distort the very fabric of space and time.
But this new event is more energetic than anything else ever seen. Designated somewhat anticlimactically as AT2021lwx, the explosion has been visible since 2020 in the constellation Vulpecula, about 8 billion light-years away.
It was first detected by the Zwicky Transient Facility (ZTF) and then the Asteroid Terrestrial-impact Last Alert System (ATLAS), both of which are designed to pick up signals from space that change in brightness over time. Usually this includes things like supernova going off or asteroids and comets whizzing around, but this was obviously something different.
“We came upon this by chance, as it was flagged by our search algorithm when we were searching for a type of supernova,” said Dr Philip Wiseman, lead researcher on the study. “Most supernovae and tidal disruption events only last for a couple of months before fading away. For something to be bright for two plus years was immediately very unusual.”
In terms of pure brightness, AT2021lwx doesn’t take the crown – that still belongs to GRB 221009A, a gamma-ray burst that washed over Earth last October in a “1 in 10,000 year event.” But that of course came and went much faster, and AT2021lwx has thrown off far more energy in total over several years.
There is another astronomical object known to maintain their brightness for long periods of time – quasars. These are supermassive black holes that are constantly and messily feeding on dust and gas, heating up the surrounding matter to brightnesses visible across the universe. But these are usually pretty steady sights in the sky.
“With a quasar, we see the brightness flickering up and down over time,” said Professor Mark Sullivan, co-author of the study. “But looking back over a decade there was no detection of AT2021lwx, then suddenly it appears with the brightness of the brightest things in the universe, which is unprecedented.”
Still, it does hint at the potential cause of AT2021lwx. The team’s leading hypothesis is that it’s a kind of supercharged quasar, with an enormous cloud of gas or dust that recently swirled into a supermassive black hole, sending shockwaves through the rest of the dust in the area.
Follow-up observations might help uncover the truth, by studying the object in different wavelengths such as X-rays. This can help determine its temperature and what else might be happening there.
The research was published in the journal Monthly Notices of the Royal Astronomical Society.
Source: Royal Astronomical Society
