Dating our galaxy’s dormant volcano

blackhole_1920A 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 companion galaxies, 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 galactic center 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 black holes generate the power seen coming from quasars and galaxies with ‘active’ centers. More here Dating our galaxy’s dormant volcano.

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