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- Astronomers studied a very bright and short-lived blue light event in space called an LFBOT.
- The brightest one found so far is named AT 2024wpp and is 1.1 billion light-years from Earth.
- Scientists discovered the event was not a supernova or a normal star explosion. Instead, it likely happened when a black hole tore apart a massive companion star.
NOIRLab published this article on December 16, 2026. Edit by EarthSky.
Bright blue cosmic outbursts
Among the more puzzling cosmic phenomena discovered over the past few decades are brief and very bright flashes of blue and ultraviolet light. These bright blue cosmic outbursts gradually fade away, leaving behind faint X-ray and radio emissions. This curious class of objects is known as luminous fast blue optical transients (LFBOTs). About a dozen have been discovered so far and astronomers wondered whether they are produced by an unusual type of supernova or by interstellar gas falling into a black hole.
Analysis of the brightest LFBOT to-date, named AT 2024wpp and discovered last year, shows that they’re neither. Instead, a team led by researchers from the University of California, Berkeley, concluded that they are caused by an extreme tidal disruption. In this case it’s where a black hole of up to 100 times the mass of our sun completely shreds its companion star within days.
Determining the processes that produce these unique light signatures tests current knowledge of the physics of black holes. And it also helps astronomers understand the evolution of stars in our Universe.
Studying this bright blue outburst
The team’s analysis of AT 2024wpp is presented in two papers recently accepted by The Astrophysical Journal Letters. The studies use data from a large collection of telescopes that measured the various wavelengths of light emitted by the LFBOT. Crucial near-infared data ware collected with the Flamingos-2 instrument on the Gemini South telescope in Chile.
Martin Still, the NSF program director for the International Gemini Observatory, said:
The ongoing discovery of luminous fast blue optical transients shows that Gemini South and other ground-based astronomical facilities are primed to characterize these mysterious objects. We expect the NSF–DOE Vera C. Rubin Observatory will spot large numbers of these transient objects, giving Gemini and other telescopes unprecedented opportunities for detailed follow-up observations.
LFBOTs got their name because they are bright – they’re visible over distances of hundreds of millions to billions of light years – and last for only a few days. They produce high-energy light ranging from the blue end of the optical spectrum through ultraviolet and X-ray. The first was seen in 2014. But the first with sufficient data to analyze wasn’t recorded until 2018. It was called AT 2018cow. The name led researchers to refer to it as the Cow. So subsequent LFBOTs have been called the Koala (ZTF18abvkwla), the Tasmanian devil (AT 2022tsd) and the Finch (AT 2023fhn). Perhaps AT 2024wpp will be known as the Wasp.
The energy emitted exceeded that of a supernova
The realization that AT 2024wpp could not have resulted from a supernova came after the 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 the conversion of about 10% of the sun’s mass into energy over a short time scale of weeks.
Specifically, the Gemini South observations revealed an excess of near-infrared light being emitted from the source. This is only the second time astronomers have observed such a phenomenon (the other case being AT 2018cow). And this is clearly not present in ordinary stellar explosions. These observations establish the near-infrared excess as a hallmark feature of FBOTs. However, no model can explain this occurrence.
Natalie LeBaron, a UC Berkeley graduate student and the first author on the paper presenting the Gemini data reported:
The sheer amount of radiated energy from 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. The main message from AT 2024wpp is that the model that we started off with is wrong. It’s definitely not just an exploding star.
It’s likely a black hole tearing its companion apart
The researchers 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 history, the black hole had been sucking material from its companion for a long time. And it completely enshrouded itself in a halo of material too far from the black hole for it to swallow.
Then, the companion star finally got too close to the black hole and was torn apart. So the new material became entrained into the rotating accretion disk and slammed against the existing material, generating X-ray, ultraviolet, and blue light. Much of the gas from the companion also ended up swirling toward the poles of the black hole, where it was ejected as a jet of material. The team calculated that the jets were traveling at about 40% of the speed of light. They also generated radio waves when they encountered surrounding gas.
Like most LFBOTs, AT 2024wpp is 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 more luminous than AT 2018cow.
The estimated mass of the companion star that was shredded was more than 10 times the mass of the sun. It may have been what’s known as a Wolf-Rayet star. That is a very hot and evolved star that has already used up much of its hydrogen. This also explains the weak hydrogen emission from AT 2024wpp.
Bottom line: Astronomers studying one of the strongest bright blue cosmic outbursts (LFBOTs) believe they occur in a binary star system where a black hole tears its companion apart.
Via NOIRLab