Gas cloud spirals into Milky Way black hole

Posted by Kate Taylor

Astronomers using ESO’s Very Large Telescope have spotted a giant gas cloud being sucked into the supermassive black hole at the heart of our galaxy.

The gas cloud, several times the mass of the Earth, is accelerating towards the black hole: over the last seven years, its speed has nearly doubled, and is now more than eight million kilometers per hour.

It's on a very elongated orbit, and in mid-2013 it will pass at a distance of only about 40 billion kilometres from the event horizon of the black hole, a distance of about 36 light-hours.

The gas cloud is much cooler than the surrounding stars - only about 280 degrees Celsius - and is composed mostly of hydrogen and helium. 

Right now, the cloud is much more dense than the hot gas surrounding the black hole. But as the cloud gets closer, it will be compressed by the increasing external pressure. At the same time, the gravitational pull from the black hole, which has a mass four million times that of the Sun, will continue to accelerate the inward motion and stretch the cloud out along its orbit.

"The idea of an astronaut close to a black hole being stretched out to resemble spaghetti is familiar from science fiction. But we can now see this happening for real to the newly discovered cloud. It is not going to survive the experience," says Stefan Gillessen of the Max-Planck-Institut für extraterrestrische Physik.

The cloud’s edges are already starting to shred and disrupt, and it's expected to break up completely over the next few years. The material is also expected to get much hotter as it nears the black hole in 2013 and it will probably start to give off X-rays.

"The next two years will be very interesting and should provide us with extremely valuable information on the behaviour of matter around such remarkable massive objects," says researcher Reinhard Genzel.