07/02/2017 7:45 PM AEDT | Updated 09/02/2017 9:52 AM AEDT

Enormous Black Hole Chews Star For a Decade

Astronomers watch the galactic equivalent of a dog with a bone.

U.S. researchers have been tracking the incredibly lengthy meal of a giant black hole consuming a star for a record-breaking decade.

And it's still not done.

Most black holes dispense of stars in a year or less. This one, spotted by University of New Hampshire scientist Dacheng Lin and his team, began devouring the star in 2005.

The phenomenon is unfolding in the center of a galaxy 1.8 billion light years from Earth, the researchers revealed in a report in Nature Astronomy. The black hole — dubbed XJ1500+0154 — has been tracked by three orbital telescopes, including NASA's Chandra X-Ray Observatory, via a sustained "tidal disruption event" in space linked to the intense gravity when a black hole rips apart and consumes a star. During such an event, some stellar debris is flung outward while the rest is sucked back into the black hole. As the star travels deeper inward to be ingested by the black hole, the material heats up to millions of degrees and generates a distinct X-ray flare. The black hole is believed to be supermassive, as are most black holes at the center of larger galaxies, notes NASA.

"We have witnessed a star's spectacular and prolonged demise," said Lin in a statement. "Dozens of tidal disruption events have been detected since the 1990s, but none that remained bright for nearly as long as this one."

Researchers don't know what it all means but are captivated by the evolution of the black hole. "For most of the time we've been looking at this object, it has been growing rapidly. This tells us something unusual — like a star twice as heavy as our sun — is being fed into the black hole," said researcher James Guillochon of the Harvard-Smithsonian Center for Astrophysics.

The black hole is expected to continue consuming its star for several years to come.

"This event shows that black holes really can grow at extraordinarily high rates," said co-author Stefanie Komossa of QianNan Normal University for Nationalities in Duyun City, China. "This may help us understand how precocious black holes came to be."