The Hungry Black Hole

G2 Is Entering the Galactic House

Simulations of the dust and gas cloud G2 on its orbit around the Milky Way central black hole SgrA*.
Photo courtesy of M. Schartmann and L. Calcada/ European Southern Observatory and Max-Planck-Institut fur Extraterrestrische Physik.

The heart of our Milky Way Galaxy is home to a black hole named Sagittarius A* (known as Sag A* for short).  It contains the equivalent of three to four million times the mass of the Sun, and as black holes, it’s kind of a quiet, friendly one. By that, I mean that it’s not constantly gulping down massive amounts of material as some other galaxies’ black holes do.  Sure, it does eat, but it seems to do so only sporadically.

Astronomers and lab physicists at the Lawrence Livermore Labs have created a supercomputer simulation showing a gas cloud called G2 which is on its way to being Sag A*’s latest snack.

Three-dimensional, volume visualization spanning the period 2010 to 2020, of the gas and dust cloud as it approaches the Sgr A* black hole near the center of the Milky Way galaxy. (Courtesy Dr. P. Chris Fragile)

They came up with six simulations showing how the event might unfold as the cloud approaches the black hole. The cloud’s makeup is still not well-understood and astronomers are still trying to figure out where it came from in the first place. It first showed up in 2002, and observers rushed to chart its size and other characteristics. The cloud appears to have a fair amount of dust that is quite warm — 500 degrees Kelvin, which is about twice as hot as Earth’s surface. The gas entrained in the cloud is superheated hydrogen and is about twice as hot as the surface of the Sun.

This cloud could be a burp of gas from an old star that was starting to lose some of its mass. Or, as some astronomers have suggested, it might have been material that didn’t quite form a planet. And, now it’s heading toward the region of the black hole, poised for a close brush with the gravity well of the black hole sometime in September 2013. As it gets nearer, the cloud will get heated to incredibly high temperatures which will make it easy to spot using radio and x-ray telescopes on Earth.

It’s likely that not all of the cloud will get sucked into the realm of the black hole. A great deal of it may pass well outside of the “point of no return” near the black hole. But, it will get shredded apart by the close encounter with the black hole’s incredibly strong gravitational pull.

Astronomers will be able to watch the black hole dally with the cloud (like a cat dallies with a mouse) for a few years. The closest approach of the cloud will take a few months, and they should be able to track as the cloud is affected by its encounter and breaks apart.




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