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Milky Way’s supermassive black hole shows increased X-ray action as mystery object passes by

Scientists are puzzled by an increased rate of X-ray flares from the giant black hole at the centre of our Milky Way Galaxy.

They are trying to determine whether it is the result of closer monitoring, or whether the flare were triggered by the close approach of a close approach of a mysterious object called G2.

The new study reveals that the black hole – Sagittarius A*, or Sgr A* for short – has been producing one bright X-ray flare about every 10 days.

In the past year, however, there has been a tenfold increase and now there is one nearly every day.

The increase took place after G2 appeared, passing close to Sgr A* in late 2013.

Originally, astronomers thought G2 was an extended cloud of gas and dust, but, apart from some stretching as it neared the black hole, its appearance did not change as expected. Some scientists now believe G2 could a star swathed in an extended dusty cocoon, but no ones really sure.

“There isn’t universal agreement on what G2 is,” said Mark Morris of the University of California at Los Angeles.

“However, the fact that Sgr A* became more active not long after G2 passed by suggests that the matter coming off of G2 might have caused an increase in the black hole’s feeding rate.”

The data has been collected by three orbiting X-ray space telescopes – NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton, with observations by the Swift satellite.

Astronomers are not all convinced the behaviour has anything to do with G2 and say the increased chatter from Sgr A* may be a common trait among black holes. For example, the increased X-ray activity could be due to a change in the strength of winds from nearby massive stars that are feeding material to the black hole.

“It’s too soon to say for sure, but we will be keeping X-ray eyes on Sgr A* in the coming months,” said co-author Barbara De Marco, also of Max Planck. “Hopefully, new observations will tell us whether G2 is responsible for the changed behaviour or if the new flaring is just part of how the black hole behaves.”

You can read more about Sagittarius A* here.

Bill Condie

Bill Condie

Bill Condie is a science journalist based in Adelaide, Australia.

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