Astrophysics: A new kind of cosmic explosion?
One of the brightest eruptions ever observed is baffling science. The explosion was brighter than a supernova, but it occurred in a galaxy where it shouldn’t have.
© NASA, ESA, CSA, M. Matsuura (Cardiff University), R. Arendt (NASA Goddard Space Flight Center and University of Maryland, Baltimore County), C. Fransson (Stockholm University), and J. Larsson (KTH Royal Institute of Technology). Image processing: a. Pagan (excerpt)
Supernovae such as 1987A are among the most violent events in the universe. But now astronomers have noticed an event that doesn’t fit the normal picture of a supernova.
AT2022aedm was a massive event: the flash in a galaxy two billion light-years away was hundreds of billions of times brighter than our Sun. But observational scientists led by Matt Nicol of Queen’s University Belfast don’t yet know what caused the massive cosmic explosion. As they write in “The Astrophysical Journal Letters.”. The duration and location of the explosion does not, in fact, correspond to a supernova, which is a prime candidate for such a luminous phenomenon.
“We’ve been looking for the most powerful cosmic explosions for more than a decade, and this is one of the brightest explosions we’ve ever seen,” Nicol says. Normally, an extremely bright supernova fades to about half its maximum value within a month. During the same period, AT2022aedm dipped to less than one percent of its peak brightness. It’s practically gone!”
The team observed the explosion for the first time using ATLAS’ network of robotic telescopes in Hawaii, Chile and South Africa. They scan the entire visible sky each night to look for objects that move or change in brightness. A few days after AT2022aedm first appeared, the working group received more data from the New Technology Telescope in Chile. These studies, along with other observations around Earth, have indicated that, contrary to all expectations, the supernova was not a possible cause.
The location of the explosion was also a big surprise. “Our data show that this event occurred in a massive red galaxy two billion light-years away. These galaxies contain billions of stars like our Sun, but none of them should be massive enough to end up in a supernova,” says Shubham Srivastav of Queen’s University. .
A comparison of historical data revealed only two other cosmic events with similar characteristics, in 2009 and 2020. And the comprehensive set of data obtained on AT2022aedm shows that it must be a new type of cosmic event. » We called this new class of light sources “Luminous Fast Coolers” or LFCs. Part of this has to do with how bright it is and how quickly it fades and cools down. Meanwhile, some researchers are big fans of Liverpool FC. “It’s a nice coincidence that our LFCs seem to favor red galaxies!” (Editor’s note: Liverpool Football Club is also called the “Reds” because of the color of the team’s home shirts.)
Nicholl and his colleagues suspect that the most likely cause of this event was the collision of a small black hole with a star. In the case of a supermassive black hole, the signal will be different again. Therefore, the search for the LFC must be intensified to prove or refute this hypothesis. Scientists want to focus on dense star clusters, where such collisions are more likely.
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