The hungry black hole
25 Oct 2012 by Evoluted New Media
A black hole in our galaxy may devour an approaching cloud of dust and gas known as G2. Supercomputer simulations suggest that some of G2 will survive the eating, but its mass will be torn apart, leaving it with a different shape and questionable future.
Computational physicists and astrophysicists from the Weapons and Complex Integration Directorate (WCI) at Lawrence Livermore National Laboratory have teamed up to produce six simulations (posted on the web) to predict the consequences of the upcoming event. The black hole (known as Sagittarius A*) in the centre of the Milky Way is 3-4 million times as big as our sun, but has been relatively quiet in terms of nebula ingestion, compared to other black holes.
“It’s not being fed very much” said Astrophysicist Stephen Murray of Sagittarius A*.
The G2 cloud was originally noticed in 2002, but the first determinations of its size and orbit only came this year. While the cloud’s make up is not very well-understood, the researchers suggest that G2 contains dust that is twice as hot as Earth’s surface and hydrogen gas that is double the temperature of the sun’s surface. However, its origin is unknown.
“The speculation ranges from it having been an old star that had kind of a burp and lost some of its outer atmosphere, to something that was trying to be a planet and couldn’t manage it because the environment was too hot,” added Murray.
As the cloud nears the black hole and begins to fall into a “gravity well” at the start of next September, it will start shedding energy causing it reach an incredibly high temperature which will make it visible to radio and X-ray telescopes on Earth.
The simulations suggest that while not all of the cloud will be eaten, as much of it will pass well outside the point of no return, it is unlikely to survive Sagittarius A*’s gravitational pull.
“There's too much dynamical friction that it experiences through hydrodynamic instabilities and tidal stretching from the black hole. So a lot of its kinetic energy and angular momentum will be dissipated away and it will just sort of break up into some sort of incoherent structure. Much of it will join the rest of the hot accretion disk around the black hole, or just fall and get captured by the black hole. It will lose a lot of its energy but not all of it. It will become so diffuse that it's unlikely that any remnant of the gas will continue on its orbital track,” concluded computational physicist Peter Anninos.
