The University of Southampton

Dr Phil Wiseman leads team witnessing the largest cosmic explosion caused by giant black hole

Published: 5 June 2023

Dr Phil Wiseman, a post-doctoral Research Fellow in Physics and Astronomy, has spearheaded a team of astronomers in observing the most significant cosmic explosion ever recorded, caused by a massive black hole. The findings of their study have been published in the Monthly Notices of the Royal Astronomical Society.

The explosion, known as AT2021lwx, has currently lasted over three years, compared to most supernovae which are only visibly bright for a few months. It took place nearly 8 billion light years away, when the universe was around 6 billion years old, and is still being detected by a network of telescopes.

Analyses conducted across a range of wavelengths, from X-rays to infra-red, revealed characteristics akin to the gravitational shredding of a star by a supermassive black hole weighing over 100 million times the mass of the sun. However, the brightness of this flare far exceeds expectations for a typical stellar disruption.

Dr Wiseman and his team have concluded that a colossal gas cloud experienced a violent disruption and was engulfed by the black hole, resulting in shockwaves propagating through the cloud remnants and the surrounding dusty "donut" structure. This extraordinary event provides a rare and explosive glimpse into the growth mechanisms of black holes.

“With new facilities, like the Vera Rubin Observatory’s Legacy Survey of Space and Time, coming online in the next few years, we are hoping to discover more events like this and learn more about them. It could be that these events, although extremely rare, are so energetic that they are key processes to how the centres of galaxies change over time.”

Dr Phil Wiseman, Physics and Astronomy, FEPS, says: ‘By meticulously analysing the light's spectrum and evaluating its distinct absorption and emission features across various wavelengths, the team successfully determined the object's distance.’

Professor Sebastian Hoenig, a co-author of the study, highlighted the significance of these calculations, stating: "Once you know the distance to the object and how bright it appears to us, you can calculate the brightness of the object at its source. Once we’d performed those calculations, we realised this is extremely bright.”

Professor Mark Sullivan, another co-author, elaborated on the uniqueness of AT2021lwx, remarking: ""With a quasar, we see the brightness flickering up and down over time. 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.” 

The research paper titled "Multiwavelength observations of the extraordinary accretion event AT2021lwx" has been published in the Monthly Notices of the Royal Astronomical Society.


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