NASA finds evidence of serial black hole eruptions

Astronomers using NASA's Chandra X-ray Observatory have found that a supermassive black hole at the centre of a group of galaxies about 105 million light years from Earth has erupted multiple times over 50 million years.
Scientists discovered the history of black hole eruptions by studying the group of galaxies named NGC 5813.
The Chandra observations are the longest ever obtained of a galaxy group, lasting for just over a week, researchers said.
Galaxy groups do not contain hundreds or even thousands of galaxies like clusters do, they are typically comprised of 50 or fewer galaxies. Like galaxy clusters, groups of galaxies are enveloped by giant amounts of hot gas that emit X-rays.

The erupting supermassive black hole is located in the central galaxy of NGC 5813.
The black hole's spin, coupled with gas spiralling toward the black hole, can produce a rotating, tightly wound vertical tower of magnetic field that flings a large fraction of the inflowing gas away from the vicinity of the black hole in an energetic, high-speed jet.

The researchers were able to determine the length of the black hole's eruptions by studying cavities, or giant bubbles, in the multi-million degree gas in NGC 5813.
These cavities are carved out when jets from the supermassive black hole generate shock waves that push the gas outward and create huge holes.

The latest Chandra observations found a third pair of cavities in addition to two that were previously found in NGC 5813, representing three distinct eruptions from the central black hole.
This is the highest number of pairs of cavities ever discovered in either a group or a cluster of galaxies.
Similar to how a low-density bubble of air will rise to the surface in water, the giant cavities in NGC 5813 become buoyant and move away from the black hole, researchers said.