Scientists say massive black hole at galactic center could awaken in 2013
when it gets closer in 2013 it will plough into the halo of hot gas around the hole"
Sorry to be pedantic, but in reality this happened 26,000 years ago, it is just that we are to observe it in 2013.
The sleeping giant at the centre of the Milky Way is about to wake up. A suicidal gas cloud is heading towards the galaxy's supermassive black
hole, which will probably swallow the cloud, generating enormous flares of radiation that could help explain why the black hole is normally so placid.
The doomed cloud was a surprise to astronomers. "We have been looking at the galactic centre for 20 years, but mainly to observe the motion of
stars," says Reinhard Genzel of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany. Genzel's colleague Stefan Gillessen
spotted the cloud in images from the Very Large Telescope array in Chile, taken in March this year. It is an unusually dense cloud, not much bigger
than our solar system and carrying about three times the mass of Earth
The team realised that the cloud also appears in earlier images, giving them a sequence that reveals its path. It is moving at almost 2500 kilometres
per second towards our galaxy's black hole, Sagittarius A*.
At present Sagittarius A* is strangely quiet, unlike quasars, the hyperactive black holes that emit huge amounts of radiation, fuelled by inflowing
gas. Our black hole gets much less gas, and for some reason this starvation state makes it much less efficient than a quasar, producing only a
thousandth as much radiation per kilogram of fuel.
While a star would just sail past our black hole unscathed, the loose mass of gas heading towards it is more vulnerable. It is already being stretched
out by the black hole's gravity, and when it gets closer in 2013 it will plough into the halo of hot gas around the hole.
That should send shockwaves through the cloud to heat it to several million degrees, and according to the group's simulations the gaseous collision
will shred the cloud into filaments. This turmoil may mean that much of the cloud ends up swirling right down into the black hole.
"By dumping more material in there, the cloud could drive the system into a higher efficiency regime," says Ginzel. There may be one huge flare of
radiation or several over the coming decades.
There's no danger of the active black hole harming Earth. And though sadly not visible to the naked eye, this radiation will give astronomers clues
as to why our black hole is normally so different from quasars.
"There is evidence that the galactic centre was more luminous within the last few thousand years, and we are unlucky in living at a time when it
appears to be unusually dormant," says astrophysicist Martin Rees at the University of Cambridge, who was not part of the study.