Using data collected by a suite of space and ground telescopes, astronomers discovered AT 2024wpp, the brightest fast blue optical transient (LFBOT) ever observed. These rare, brief, intensely bright explosions have intrigued scientists for a decade, but the extreme brightness and detailed multi-wavelength data from AT 2024wpp show that they cannot be explained by any sort of normal stellar explosion such as a supernova. Instead, the new observations indicate that AT 2024wpp was powered by an extreme tidal disruption event in which a black hole of about 100 times the mass of the Sun tore apart a massive companion star in a matter of days, converting an extraordinary fraction of the star’s mass into energy.
This composite image presents radiological and optical data from the LFBOT AT 2024wpp event. Image credit: NASA / CXC / UC Berkeley / Nayana and others. / Legacy Survey / DECaLS / BASS / MzLS / SAO / P. Edmonds / N. Wolk.
LFBOTs get their name because they are bright (they are visible at distances ranging from hundreds of millions to billions of light years) and last only a few days.
They produce high-energy light ranging from the blue end of the optical spectrum to ultraviolet and X-rays.
The first was observed in 2014, but the first with enough data to analyze was recorded in 2018 and, by standard naming convention, was called AT 2018cow.
The name led researchers to call it the Cow, and later LFBOTs have been called, ironically, the Koala (ZTF18abvkwla), the Tasmanian Devil (AT 2022tsd), and the Finch (AT 2023fhn). Maybe AT 2024wpp will be known as Wasp.
The realization that AT 2024wpp could not have resulted from a supernova came after researchers calculated the energy it emitted.
It turned out to be 100 times greater than what would be produced in a normal supernova.
The radiated energy would require converting about 10% of the Sun’s rest mass into energy over a very short period of a few weeks.
Specifically, Gemini South observations revealed excess near-infrared light emitted by the source.
This is only the second time astronomers have observed such a phenomenon – the other case being AT 2018cow – which is clearly not present in ordinary stellar explosions.
These observations establish near-infrared excess as a distinctive feature of FBOTs, although no model can explain this event.
“The amount of energy radiated by these bursts is so large that you can’t power them with a core collapse stellar explosion — or any other type of normal stellar explosion,” said Natalie LeBaron, a graduate student at the University of California, Berkeley.
“The main message of AT 2024wpp is that the model we started with is wrong. It’s certainly not just a star exploding.”
Scientists hypothesize that the intense, high-energy light emitted during this extreme tidal disruption was a consequence of the long parasitic history of the black hole binary system.
As they reconstruct this story, the black hole had long been sucking matter from its companion, completely enveloping itself in a halo of matter too far from the black hole for it to swallow.
Then, when the companion star finally got too close and was torn apart, the new material was pulled into the spinning accretion disk and collided with the existing material, generating X-rays, ultraviolet, and blue light.
Much of the companion’s gas also ended up swirling toward the black hole’s poles, where it was ejected as a jet of material.
The authors calculated that the jets traveled at about 40% the speed of light and generated radio waves when they encountered the surrounding gas.
Like most LFBOTs, AT 2024wpp is located in a galaxy with active star formation, so large stars like these are expected.
AT 2024wpp is 1.1 billion light years away and between 5 and 10 times brighter than AT 2018cow.
The estimated mass of the companion star that was shredded was more than 10 times the mass of the Sun.
“This may be what is called a Wolf-Rayet star, which is a very hot, evolved star that has already used up much of its hydrogen,” the astronomers said.
“This would explain the low hydrogen emissions of the AT 2024wpp.”
The results appear in two articles in the Astrophysical journal letters.
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Natalie LeBaron and others. 2025. The brightest known fast blue optical transient at 2024wpp: unprecedented evolution and properties in the ultraviolet to near-infrared. ApJLin press; arXiv:2509.00951
AJ Nayana and others. 2025. The brightest known fast blue optical transient at 2024wpp: unprecedented evolution and properties in X-ray and radio. ApJLin press; arXiv:2509.00952
