Using data collected by a complex of space-based and ground-based telescopes, astronomers have discovered AT 2024wpp, the brightest fast blue optical transient (LFBOT) ever observed. These rare, brief and very bright bursts have puzzled scientists for a decade, but the extreme brightness and detailed multi-wavelength data of AT 2024wpp show that they cannot be explained by any ordinary stellar explosion such as a supernova. Instead, the new observations show that AT 2024wpp was caused by an extreme tidal disruption in which a black hole with about 100 times the mass of the Sun tore apart a massive companion star in a matter of days, converting an extraordinary portion of the star's mass into energy.
This composite image shows X-ray and optical data from the LFBOT event at 2024wpp. Image credit: NASA/CXC/UC Berkeley/Nayana etc.. / Legacy Survey / DECaLS / BASS / MzLS / SAO / P. Edmonds / N. Volk.
LFBOTs get their name because they are bright—seen at distances of 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 spotted in 2014, but the first with enough data to analyze was reported in 2018 and, according to standard naming convention, called AT 2018cow.
This name led researchers to call it Cow, and subsequent LFBOTs were jokingly called Koala (ZTF18abvkwla), Tasmanian Devil (AT 2022tsd) and Finch (AT 2023fhn). Perhaps AT 2024wpp will be called Wasp.
The realization that AT 2024wpp could not have arisen from a supernova explosion came after researchers calculated the energy it emitted.
It turned out to be 100 times larger than what would have occurred during an ordinary supernova.
The energy emitted would require converting about 10% of the Sun's rest mass into energy in a very short period of time of a few weeks.
In particular, observations of Gemini South disclosed excess near-infrared light emitted by a source.
This is only the second time that astronomers have observed such a phenomenon (the second being AT 2018cow), which is clearly not found in ordinary stellar explosions.
These observations indicate that near-infrared excess is a hallmark of FBOT, although no model can explain this phenomenon.
“The amount of energy emitted from these bursts is so large that you can't power them with a core-collapse stellar explosion—or any other type of regular 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. This is definitely not just an exploding star.”
Scientists speculate that the intense, high-energy light emitted during this extreme tidal disruption was a consequence of the long parasitic history of the binary black hole system.
As they reconstruct the story, the black hole spent a long time sucking material out of its companion, completely enveloping itself in a halo of material too far from the black hole for it to swallow.
Then, when the companion star finally got too close and was torn apart, new material was pulled into the rotating accretion disk and collided with existing material, generating X-rays, ultraviolet and blue radiation.
Much of the gas from the companion also ended up swirling toward the black hole's poles, where it was ejected as a jet of material.
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 such large stars are expected.
AT 2024wpp is 1.1 billion light-years away and 5 to 10 times brighter than AT 2018cow.
The estimated mass of the destroyed companion star was more than 10 times the mass of the Sun.
“It may have been a Wolf-Rayet star, a very hot and advanced star that had already used up most of its hydrogen,” the astronomers said.
“This could explain the weak hydrogen emission from AT 2024wpp.”
The results were published in two journal articles Letters in an astrophysical journal.
_____
Natalie LeBaron etc.. 2025. Brightest known fast blue optical transient AT 2024wpp: unprecedented evolution and properties from ultraviolet to near-infrared. ApJLin print; arXiv: 2509.00951
AJ Nayana etc.. 2025. Brightest known fast blue optical transient AT 2024wpp: unprecedented evolution and properties in X-rays and radio. ApJLin print; arXiv: 2509.00952
