Dating our galaxy’s dormant volcano

An artist’s conception of a black hole generating a jet. Two million years ago the supermassive black hole at the center of our galaxy was 100 million times more powerful than it is today. Credit: NASA/Dana Berry/SkyWorks Digital Read more at: http://phys.org/news/2013-09-dating-galaxy-dormant-volcano.html#jCp

An artist’s conception of a black hole generating a jet. Two million years ago the supermassive black hole at the center of our galaxy was 100 million times more powerful than it is today. Credit: NASA/Dana Berry/SkyWorks Digital

A dormant volcano—a supermassive black hole—lies at the heart of our galaxy. Fresh evidence suggests that it last erupted two million years ago.

Astronomers have long suspected such an outburst occurred, but this is the first time they’ve been able to date it.

The evidence comes from a lacy filament of gas, mostly hydrogen, called the Magellanic Stream. This trails behind our galaxy’s two small , the Large and Small Magellanic Clouds.

“For twenty years we’ve seen this odd glow from the Magellanic Stream,” said Professor Joss Bland-Hawthorn, an ARC Federation Fellow at the University of Sydney, Australia, and a Fellow at the Australian Astronomical Observatory, who led a team studying this problem.

“We didn’t understand the cause. Then suddenly we realized it must be the mark, the fossil record, of a huge outburst of energy from the center of our galaxy.”

“It’s been long suspected that our  might have sporadically flared up in the past. These observations are a highly suggestive ‘smoking gun’,” said Martin Rees, Astronomer Royal, who was one of the first people to suggest that  generate the power seen coming from quasars and galaxies with ‘active’ centers.

The team gives its arguments in a paper accepted for publication in The Astrophysical Journal. Professor Bland-Hawthorn will speak about the work at the Galaxy Zoo meeting in Sydney, Australia, on 24 September….

Read more at: http://phys.org/news/2013-09-dating-galaxy-dormant-volcano.html#jCp

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