They have been recording their light for three years, when most supernovae are barely visible for a few months
For three years astronomers have been observing its light. This is the biggest cosmic explosion ever seen. and that it could be the result of a vast cloud of gas, perhaps thousands of times larger than the Sun, violently altered by a supermassive black hole. The explosion, cataloged as AT2021lwx and which occurred almost 8 billion light years agowhen the universe was about 6,000 million, is described in a study led by the University of Southampton published today Monthly Notices of the Royal Astronomical Society.
Most supernovae (the explosion of a dying star and one of the largest known) are visible for a few months, however the one now described was located three years ago and is still being detected by a network of telescopes. This huge explosion is ten times brighter than any known supernova and three times brighter than the brightest tidal disruption event, in which a star falls into a supermassive black hole.
Investigators believe the explosion is the result of a very rare event: a vast cloud of gas, possibly thousands of times larger than our Sun, that has been violently disturbed by a black hole supermassive. That way, fragments of the gas cloud would be being swallowed by the black hole, sending shock waves through its remains and the dusty outline of the hole.
Last year, astronomers witnessed the brightest explosion on record: a gamma-ray burst known as GRB 221009A, which occurred 2 billion light-years from Earth. That burst was brighter than the one described now, but it only lasted a fraction of the time, which means that the total energy released by AT2021lwx is much higher.
The outbreak was detected in 2020 by the Zwicky Transient Facility and later by the Asteroid Terrestrial Impact Last Alert System (ATLAS), both in the United States and in charge of monitoring the sky to detect objects that rapidly change brightness, which indicates the existence of cosmic events. “We discovered it by chance,” said University of Southampton researcher Philip Wiseman, who noted that “something that shined for more than two years was immediately very unusual.”
For this reason, the object continued to be investigated with the Gran Telescopio de Canarias; the New Technologies Telescope (operated by the European Southern Observatory) in Chile, and the Neil Gehrels Swift (a collaboration between NASA, the UK and Italy). Using various data, the team was able to measure the distance to the object. Once that parameter is known and how bright it appears, the brightness of the object at its source can be calculated. “Once those calculations were made, we realized that it is extremely bright,” said Sebastian Hönig, who is also a signatory to the research, quoted by the University of Southampton.
The only objects in the universe as bright as AT2021lwx are quasars, supermassive black holes with a constant stream of gas falling on them at high speeds. In a quasar, the brightness waxes and wanes over time, but in the case of this explosion, it had gone undetected a decade ago and “suddenly appears as bright as the brightest things in the universe, which is unprecedented.” added study co-author Mark Sullivan.
The team now wants to collect more data about the explosion, measuring different wavelengths, including X-rays, which could reveal the object’s surface and temperature, as well as underlying processes. They will also carry out enhanced computer simulations to see if they match their theory of the cause of the explosion.