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Wednesday, May 27, 2009

Mega-Telescope Net To Stare Down Massive Black Hole At Center of Milky Way

6a00d8341bf7f753ef00e54f418f828834-800wi Scientists are setting up a super-telescope-network to study Sagittarius A*, the suspected black hole at the center of our galaxy. It's eight terra-yotta-kilograms , aka "so vast we don't even have prefixes that high", four million solar masses. So why is it so hard to see? Well, it's buried behind half a galaxy's worth of light-emitting stars, interstellar dust over thirty thousand light years kind of reduces the signal, and - minor issue - black holes eat light. Which makes things trickier.

Luckily astronomer Shep Doeleman of MIT remembers Voltron, and realized that if one telescope isn't enough, you just plug more of them together until it works. The technique is called Very Long Baseline Interferometry, VLBI, and it effectively creates a vast virtual dish as big as the distance between the telescopes - and he's using telescopes all over the planet.

The second part of his strategy is tuning the telescopes to 1 mm radiation, which is not as strongly absorbed by the half-a-galaxy's worth of junk between us and the action. And what action it is - if we can observe Sagittarius A*'s surroundings we can confirm once and for all whether it's a black hole - and prove Einstein right (or wrong!)

Relativity describes how large masses can bend space, and a black hole is where the mass is so large that space gives up altogether and becomes a singularity. Black holes are already well understood, we think, but we've only ever observed them at second hand - the behavior of orbiting objects or bent light rays. To actually view the shadow of a black hole, the cut-off point where light is swallowed and cannot escape, would be a massive advance - and only the beginning.

Detailed observation of the area around the Sag A* border would be a goldmine of information. The spin and rate of matter inflow into the central black hole will tell us about the Milky Way's creation, as well as providing further extreme tests of general relativity. We could even see frame dragging, which sounds like a video game hardware issue but is actually something that could happen to reality - where a spinning black hole grabs hold of space and literally pulls reality around after it.

Posted by Luke McKinney.