Spiralling towards destruction

Normal, Weekender

The National, Friday 06th July, 2012

NEXT year will see one of the biggest collisions ever observed by man.
A giant gas cloud will hit the mas¬sive black hole – known as Sagittarius A – which lies at the centre of our galaxy in 2013.
Actually, the cloud will miss by quite a distance – 24,000,000,000 miles to be semi-exact – and while this is quite a distance (indeed it takes light 36 hours to travel that far), the tidal forces of the black hole will rip the gas cloud apart.
One observer will be Stefan Gillessen, an astrophysicist at the Max Planck Institute for Extraterrestrial Physics in Munich, Ger¬many, who has been observing the black hole for the last 20 years.
He said, "So far there were only two stars that came that close to Sagittarius A. They passed unharmed, but this time will be dif¬ferent; the gas cloud will be completely ripped apart by the tidal forces of the black hole."
As the cloud gets closer, it’s speed gets quicker – it has doubled its speed in just seven years.
Astronomers using ESO’s Very Large Telescope will also watch the black hole.
Colleague Reinhard Genzel at the Max- Planck Institute for Extraterrestrial Physics has discovered a unique new object fast ap¬proaching the black hole.
Gillessen said, "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," ex¬plains Stefan Gillessen, the lead author of the paper.
The gas cloud will pass at a distance of only about 40 billion kilometers from the event horizon of the black hole, a distance of about 36 light-hours, very close, when it’s an encounter with an object as powerful and destructive as a supermassive black hole.
As it approaches its doom, the cloud is glowing under the strong ultraviolet radiation from the hot stars around it in the crowded heart of the Milky Way.
As the cloud gets ever closer to the hungry beast, increasing ex¬ternal pressure will compress the cloud.
At the same time the huge 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 cloud’s edges are already starting to shred and disrupt and it is expected to break up completely over the next few years. The astronomers can already see clear signs of increasing disruption of the cloud over the period between 2008 and 2011.
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. There is currently little material close to the black hole so the newly-arrived meal will be the dominant fuel for the black hole over the next few years.
One explanation for the formation of the cloud is that its material may have come from nearby young massive stars that are rapidly losing mass due to strong stellar winds. Such stars literally blow their gas away. Colliding stellar winds from a known double star in orbit around the central black hole may have led to the formation of the cloud.
"The next two years will be very interesting and should provide us with extremely valuable informa¬tion on the behavior of matter around such remark¬able massive objects," says Genzel.-Mail Online