(Phys.org) —University of Michigan astronomers could be the first to witness a rare collision expected to happen at the center of the galaxy by spring.


The galactic center as imaged by the Swift X-ray Telescope. This image is a montage of all data obtained in the monitoring program from 2006-2013. Credit: Nathalie Degenaar Enlarge

With NASA's orbiting Swift telescope, the U-M team is taking daily images of a mysterious gas cloud about three times the mass of Earth that's spiraling toward the  at the Milky Way's core. From our vantage point, the core lies more than 25,000 light years away in the southern summer sky near the constellations Sagittarius and Scorpius.

The , called G2, was discovered by  in Germany in 2011. They expected it to hit the black hole, called Sagittarius A* (pronounced Sagittarius A-star by astronomers), late last year. That didn't happen, but the cloud continues to drift closer. Astronomers now predict that the impact will occur in the next few months.

Astronomers have never seen anything like this, much less with a front-row seat.

"Everyone wants to see the event happening because it's so rare," said Nathalie Degenaar, who leads this imaging effort as a Hubble research fellow in the Department of Astronomy at the College of Literature, Science, and the Arts.

Supermassive  are believed to lurk at the centers of all elliptical and spiral galaxies. The Milky Way's, by comparison, is dim—about a hundred million times fainter than scientists might expect. But it's likely the more common variety, Degenaar said.

"We think that the fainter ones are the majority, but it's very difficult to study those," she said. "We just can't see them. Ours is the only one we can study to understand what their role is in the universe."

The collision will give astronomers a unique opportunity to see how faint supermassive black holes feed and perhaps why they don't consume matter in the same way as their brighter counterparts in other galaxies. While black holes themselves are invisible and don't permit light to escape, the material falling into them shines in X-rays.

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