"The eruption, which has lasted for more than 100 million years, has generated energy equivalent to hundreds of millions of gamma-ray bursts," said the US space agency in a statement.

The discovery was made by NASA's orbiting Chandra X-ray Observatory which is controlled from a base in Cambridge, Massachusetts.

The huge eruption was seen in a Chandra image of the hot, X- ray emitting gas of a galaxy cluster called MS 0735.6+7421, the agency said. The galaxy is about 2.6 billion light years away.

Scientists believe that this black hole is a relatively recent phenomena.

This event was caused by gravitational energy release, as enormous amounts of matter fell toward a black hole. Most of the matter was swallowed, but some of it was violently ejected before being captured by the black hole.

"I was stunned to find that a mass of about 300 million suns was swallowed," said Brian McNamara of Ohio University, lead author of a study on the discovery published in the latest issue of Nature.

The energy released shows the black hole in MS 0735 has grown dramatically during this eruption. Previous studies suggest other large black holes have grown very little in the recent past, and that only smaller black holes are still growing quickly.

"This new result is as surprising as it is exciting," said co-author Paul Nulsen of the Harvard-Smithsonian Center for Astrophysics in Cambridge. "This black hole is feasting, when it should be fasting."

Gas is being pushed away from the black hole at supersonic speeds over a distance of about a million light-years, said the scientists. The mass of the displaced gas equals about a trillion suns, more than the mass of all the stars in the Milky Way.

"Until now we had no idea this black hole was gorging itself," said Michael Wise of the Massachusetts Institute of Technology in Cambridge. "The discovery of this eruption shows X-ray telescopes are necessary to understand some of the most violent events in the universe."

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