Astronomers have captured the brightest light ever observed from a giant black hole at the center of a distant galaxy. A star more than 30 times the mass of the sun approached the black hole, was torn to pieces by gravity, and the aftermath produced a powerful flash.
A research team led by Professor Matthew Graham of the Division of Physics, Mathematics and Astronomy at Caltech said on the 4th (local time) in the international journal Nature Astronomy that they observed the largest flash on record, which occurred in a supermassive black hole at the center of a galaxy 20 billion light-years from Earth (a light-year is the distance light travels in one year, about 9.46 trillion km).
The team analyzed that the phenomenon was caused by a tidal disruption event (TDE). A TDE is when a star close to a black hole is pulled with different gravitational forces depending on its position and is torn apart. Like a ship that shatters in an instant when caught in a fierce whirlpool, a massive star was smashed to pieces in front of the black hole.
A black hole is a celestial object with gravity so strong that it pulls in all matter. Even light cannot escape, hence the name black hole. However, some of the star swallowed by the black hole is emitted as electromagnetic energy (light). The team said the total ultraviolet and visible light energy released this time is comparable to the energy produced when the mass of one sun is completely converted into light. Even in the universe, events in which such a large amount of energy is released at once are extremely rare.
The team first discovered this light source in 2018. At the time, they regarded it as a common explosion from a nearby galaxy. But follow-up observations in 2023 confirmed that the light was emitted about 10 billion years ago, and, considering the expansion of the universe, the region is now about 20 billion light-years from Earth. In other words, what happened 10 billion years ago has only now reached our eyes.
The location where the light originated is an active galactic nucleus (AGN), where a supermassive black hole at a galaxy's center draws in surrounding matter and emits light. The source's brightness increased by more than 40 times right after the explosion, and it was found to be about 30 times stronger than the most powerful AGN outburst reported to date. It was so bright that the team nicknamed the event "Superman."
Around a black hole, an accretion disk forms as gas and dust are pulled in by gravity and rotate. It has long been predicted that very massive stars could be born there, but there had been no direct evidence. This observation is regarded as the most compelling case yet suggesting the presence of a giant star in the accretion disk around a supermassive black hole.
This means the area around a black hole may not be a quiet darkness but a dynamic cosmic jungle where stars are born, torn apart and swallowed. Graham said, "Black holes are far more dynamic than we think," adding, "It will take a long time to fully understand this phenomenon."
Long-term monitoring is still needed to find out how this event will conclude. Because the source is so far away, what happened there over two years is seen on Earth only about seven years later. We are effectively watching the scene of a star being swallowed by a black hole in quarter-speed slow motion.
References
Nature Astronomy (2025), DOI: https://doi.org/10.1038/s41550-025-02699-0