For the first time, astronomers have spotted a black hole's lunch before it gets eaten.
A cloud of gas is being pulled closer to the supermassive black hole* lurking in the center of our galaxy, 27,000 light-years away. This unprecedented discovery is being monitored by an international team of scientists using the European Southern Observatory's Very Large Telescope (VLT).
The cool cloud — composed mainly of hydrogen and helium, with a mass three times that of Earth — has been picking up speed and by 2013, astronomers will hopefully see some fireworks. By then, the first wisps of gas should be sucked into the black hole's event horizon, causing the black hole to flare brightly.
The cloud is currently charging in the direction of the black hole at 2,350 kilometers per second — twice the speed it was traveling seven years ago.
"The next two years will be very interesting and should provide us with extremely valuable information on the behavior of matter around such massive objects, and its ultimate fate," said co-investigator Reinhard Genzel, of UC Berkeley and the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, Germany.
Once the astronomers had calculated the trajectory of the cloud, they realized it would pass within 40 billion kilometers (25 billion miles) of the black hole behemoth — that's approximately 250 times the sun-Earth distance.
Stars can whiz past the black hole at this distance without too much trouble, but a cloud of gas will undergo intense tidal forces and get shredded. It will become unstable and spiral into the black hole.
According to the researchers, the cloud is already beginning to show signs of turbulence and its future is grim. "It is not going to survive the experience," emphasized lead scientist Stefan Gillessen of the MPE.
Although our galaxy's supermassive black hole — weighing in at 4.3 million times the mass of our sun — has gravitational dominance over the stars orbiting it in the Milky Way's core, there's surprisingly little activity. Very few stars venture close to the black hole and matter falling into it is at a premium. Since 1992, only two stars have been observed to stray as close as the gas cloud will in 2013.
But this period of quiescence is about to change.
As the gas falls into its death spiral, it will get stretched out and experience rapid heating as it interacts with the gases surrounding the black hole's accretion disk. As more matter feeds the disk, it is predicted that X-ray emissions will cause the region near the event horizon to blast X-rays hundreds or thousands of times their usual intensity, which will be easily detectable.
Some of the gas will be ejected from the black hole, to continue its orbit, but it will never be the same again.
Beginning in 2012, space observatories like NASA's Chandra X-ray Space Telescope will be attentively staring into the core of our galaxy, watching the black hole picnic unfold.
Gillessen's team's work is set to appear in the Jan. 5 edition of the journal Nature.
*Just in case you were waiting for me to mention Muse and a certain song about a rather large black hole… here you go!
Image: A screenshot of a simulation of the black hole encounter — after close approach, the cloud will be a turbulent mess. Credit: ESO/MPE/M. Schartmann/L. Calçada