Researchers at the University of New Hampshire have discovered a huge black hole that tore apart a nearby star and continued to feed off its remains for nearly ten years. This black hole feeding frenzy is more than 10 times longer than any other event of a star’s death that has been witnessed.
Dacheng Lin, a research scientist at UNH’s Space Science Center and the study’s lead author, witnessed the event and described the star’s death as prolonged and spectacular. He added that although a fair number of these ‘tidal disruption’ events have been detected since the 1990s, none continued to be bright for nearly as long as this one.
The team used data from three orbiting X-ray telescopes – ESA’s XMM-Newton and NASA’s Swift Satellite and Chandra X-ray Observatory, and found evidence of a gigantic “tidal disruption event” (TDE). Tidal forces generated by the powerful gravity from a black hole can destroy an object, such as a star, that ventures too close. During a tidal disruption event, some of the stellar debris falls toward the black hole, while the rest is flung outward at high speeds. The debris falling toward the black hole is consumed and is heated up to millions of degrees. This generates a distinct X-ray flare.
The multi-wavelength flares can be seen by the satellites and helps scientists to study massive back holes that are otherwise dormant. Previous flares that were observed were short lived and normally becoming very faint within a year. This super long X-ray flare has however remained bright for close to a decade. The unusually long, bright phase of this TDE means that this was either the first where a smaller star was completely torn apart during one of these events, or the most massive star ever to be torn apart. The X-ray source containing this black hole is situated in a small galaxy approximately 1.8 billion light years from Earth and is known by the abbreviated name XJ1500+0154.
The Eddington limit is defined by a balance between the inward pull of the gravity of the black hole and the outward pressure of radiation from the hot gas. The X-ray data in this case shows that radiation from material surrounding this black hole surpasses the Eddington limit consistently.
The researchers concluded that supermassive black holes could grow at rates above those corresponding to the Eddington limit. This growth may result from TDEs, or perhaps other means. Either way, the conclusion has important implications, as it may help explain how supermassive black holes managed to reach masses about a billion times larger than the sun when the universe was only about a billion years old.
Based on the modeling done, the researchers predict that XJ1500+0154’s feeding supply should be reduced considerably in the next decade. That will result in the flare starting to fade in the next number of years.
The full study was published in Nature Astronomy.