Black Holes Shred Massive Stars Creating Mysterious Blue Cosmic Explosions

Decade-Long Mystery Finally Solved

For nearly a decade, astronomers have been puzzled by brief, intensely bright flashes of blue light that appear without warning in deep space. Just over a dozen of these Luminous Fast Blue Optical Transients (LFBOTs) have been discovered to date, and their cause has puzzled astronomers for around a decade . Previous suspects have included strange types of exploding stars (supernovas) and interstellar gas being gobbled up by black holes . Now, scientists believe they've cracked the code behind these cosmic enigmas.

At the heart of the discovery is a signal from a so-called Luminous Fast Blue Optical Transient (LFBOT), designated AT 2024wpp, first spotted in 2024 . Last year, astronomers detected the most luminous LFBOT ever observed, dubbed AT 2024wpp. Located around 1.1 billion light-years from Earth, it outshone previous examples and gave researchers their clearest look yet at what powers these events . This breakthrough observation provided the missing piece of the puzzle.

"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," says Natalie LeBaron, UC Berkeley graduate student and first author on the paper presenting the Gemini data . It turned out to be 100 times greater than what would be produced in a normal supernova, which would require the conversion of about 10% of the rest-mass of the sun into energy over a very short time scale, mere weeks .

The Violent Reality Behind the Light Show

The signal revealed to a team of scientists that LFBOTs are the result of extreme Tidal Disruption Events (TDEs), in which a black hole with a mass up to 100 times that of the sun, completely shreds a companion star in just a matter of days . This isn't your typical black hole feeding scenario. The team theorizes that in the case of the TDE behind AT 2024wpp, the black hole has been parasitically feeding from a companion star for a long time. This resulted in the black hole being completely encased in a spherical shell of material. However, this shell is too far away from the black hole to be devoured by it .

However, the companion star eventually spirals close enough to the black hole to be spaghettified by its immense gravitational influence. This results in new stellar material slamming into the matter that the black hole has been stealing throughout the system's history. This generated X-ray, ultraviolet, and optical blue light, seen as AT 2024wpp . The process is both violent and spectacular, creating some of the most energetic events in the known universe.

Radio waves are generated when material from around the black hole is channelled to its poles, where it is accelerated to around 40% the speed of light and blasted out as jets . The team estimated that the star shredded in the event that launched AT 2024wpp has a mass around 10 times that of the sun and was a highly evolved star nearing the end of its life, called a Wolf-Rayet star, explaining the weak hydrogen emission seen around AT 2024wpp .

Implications for Black Hole Science

This discovery carries significant implications for our understanding of black hole physics and stellar evolution. The inferred mass of the black hole — in a range sometimes referred to as intermediate-mass black holes — is also intriguing for astronomers. While black holes of more than 100 solar masses are known to exist because their mergers have been detected by gravitational wave experiments like the Laser Interferometer Gravitational-Wave Observatory (LIGO), they've never been directly observed and how they grow to that size is still a mystery .

Raffaella Margutti, an associate professor of astronomy and physics at UC Berkeley, says these events offer a new way to study how black holes form and grow. "Theorists have come up with many ways to explain how we get these large black holes, to explain what LIGO sees," she said . The research provides a new window into understanding the evolution of massive stars and their relationship with black hole companions.

Figuring out the processes that produce these unique light signatures tests current knowledge of the physics of black holes and helps astronomers understand the evolution of stars in our Universe . Study of this and similar events could shed light on the stellar environment in which large black holes evolve alongside a massive stellar companion .

Looking Beyond the Blue Flash

The breakthrough came from analyzing AT 2024wpp across multiple wavelengths of light, from X-rays to radio waves. The team's analysis of AT 2024wpp is presented in two papers recently accepted by The Astrophysical Journal Letters. The studies utilize data from a large collection of telescopes that measured the various wavelengths of light emitted by the LFBOT . This comprehensive approach allowed scientists to piece together the complete picture