ASTRONOMER IDENTIFIED THE LARGEST COSMIC EXPLOSION THAT HAS EVER BEEN OBSERVED

The NGC 6946, a spiral galaxy about 22 million light years away from Earth, also referred to as the ‘Fireworks Galaxy’. [File: NASA]

Fri 12 May 2023:

The largest cosmic explosion ever seen has been found by astronomers; it is a fireball 100 times the size of our Solar System that abruptly started burning more than three years ago in the far reaches of the universe.

The scientists stressed that additional research was necessary to fully comprehend the mysterious phenomena even though they provided what they believe to be the most plausible explanation for the explosion on Friday.

The explosion, known as AT2021lwx, has currently lasted more than three years, compared with most supernovae which are only visibly bright for a few months, according to a study published in Monthly Notices of the Royal Astronomical Society.

Led by the University of Southampton, the astronomers believe the explosion is a result of a vast cloud of gas, possibly thousands of times larger than our sun, that has been violently disrupted by a supermassive black hole.

According to the study, the explosion took place nearly 8 billion light years away, when the universe was about 6 billion years old and is still being detected by a network of telescopes.

Such events are very rare and nothing on this scale has been witnessed before, the researchers say.

Last year, astronomers witnessed the brightest explosion on record: GRB 221009A, a gamma-ray burst called BOAT (Brightest Of All Time).

Although BOAT was brighter than AT2021lwx, it only lasted a fraction of the time, implying that the overall energy produced by the AT2021lwx explosion was far bigger.

Researchers have dubbed AT2021lwx “Scary Barbie” due to its “terrifying energy.”

According to Danny Milisavljevic, assistant professor of Physics and Astronomy at Purdue University, AT2021lwx was first assigned a random alphanumeric name when discovered: ZTF20abrbeie. The “Scary Barbie” nickname came from its alphanumeric designation “abrbeie” and “scary” because of its power.

We first thought AT2021lwx aka ZTF20abrbeie aka #ScaryBarbie was a superluminous supernova from a massive star. But no theoretical models came close to explaining the terrifying energy output that continues to this day. A supermassive black hole seems to be the only solution. pic.twitter.com/GldfFWltJc

— Danny Milisavljevic (@astro_dan_mil) April 26, 2023

AT2021lwx was discovered by the Zwicky Transient Facility in California in 2020 and was later caught up by the Asteroid Terrestrial-impact Last Alert System (ATLAS) in Hawaii.

However, the magnitude of the explosion was unknown until today.

Philip Wiseman, research fellow at the University of Southampton, who led the research, said: “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.”

It was only when astronomers, including Wiseman, looked at it through more powerful telescopes that they realised what they had on their hands. By analysing different wavelengths of light, they worked out that the explosion was roughly 8 billion light years away. That is much farther than most other new flashes of light in the sky, which means the explosion behind it must be far greater.

It is estimated to be about 2 trillion times brighter than the Sun, Wiseman said.

Astronomers have looked into several possible explanations. One is that AT2021lwx is an exploding star – but the flash is 10 times brighter than any previously seen “supernova”.

Another possibility is what is called a tidal disruption event, when a star is torn apart as it is sucked into a supermassive black hole. But AT2021lwx is still three times brighter than those events and Wiseman said their research did not point in this direction.

The only somewhat comparable bright cosmic event is a quasar, which happens when supermassive black holes swallow huge amounts of gas in the centre of galaxies. But they tend to flicker in brightness, Wiseman said, whereas AT2021lwx suddenly started flaring up from nothing three years ago and it is still blazing away.

“This thing we have never, ever seen before – it just came out of nowhere,” Wiseman said.

Now that astronomers know what to look for, they are monitoring the skies for other similar explosions

SOURCE: INDEPENDENT PRESS AND NEWS AGENCIES

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