UNH scientists make an ‘out of this world’ discovery

Bret Belden

Scientists at the University of New Hamphire’s Space Science Center have discovered that a massive black hole has torn apart a star and has now been feeding on it for over 10 years. The black hole in question, XJ1500+0154, is found in a small galaxy about 1.8 billion light-years from Earth.

When a star wanders too close to a black hole, it is ripped apart by intense gravitational tides in a process referred to by scientists as a “tidal disruption event” (TDE). A portion of the star’s debris will be flung outward, while the rest is corralled into a disk that swirls into the black hole and becomes rapidly heated to temperatures reaching millions of degrees. This heated reaction causes a unique X-ray flare, distinguishing it as a TDE.

“Dozens of these so-called ‘tidal-disruptions’ events have been detected since the 1990s, but none that remained bright for nearly as long as this one,” said UNH Space Science Center research scientist and the study’s lead author Dacheng Lin said in a UNH Today press release that was published on Feb. 6.

With the aid of three orbiting X-ray telescopes, European Space Agency’s XMM-Newton, and NASA’s Chandra X-Ray Observatory and Swift Satellite, researchers were able to locate the distinct multi-wavelength flares of this particular massive TDE that began in July 2005. The extraordinary length of this X-ray flare currently has scientists speculating as to if this is the most massive star to have ever been ripped apart by a black hole. These powerful telescopes will allow the scientists to continue monitoring the star’s demise.

“We have witnessed a star’s spectacular and prolonged demise,” said Lin in the press release.

The galactic feeding frenzy by the black hole is record breaking. Not only has it been the longest known instance of a black hole devouring a star, but this particular TDE has also been noted to consistently surpass the Eddington Limit, the first observation of an event of this kind. The Eddington Limit is a point in time where the material surrounding the black hole finds a balance between the inward pull of the black hole’s gravity and the outward pressure of radiation from the hot gasses. The X-rays coming from this black hole also indicate that it appears to be growing as it ingests the star. By the current rate of this star’s depletion, researchers estimate the feast will continue for another decade, until the star is no more.

For more information on this discovery, you can read Lin’s published paper describing these results in the Feb. 6 issue of the journal “Nature Astronomy.”