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Old 05-30-2012, 03:31 PM
 
Location: Texas
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"These faint jets are a ghost or after-image of what existed a million years ago," said Meng Su, an astronomer at the Harvard-Smithsonian Center for Astrophysics (CfA), and lead author of a new paper in the Astrophysical Journal.



"They strengthen the case for an active galactic nucleus in the Milky Way's relatively recent past," he added.

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Old 05-30-2012, 05:54 PM
 
Location: Wasilla, Alaska
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Quote:
Originally Posted by Brian.Pearson View Post
"These faint jets are a ghost or after-image of what existed a million years ago," said Meng Su, an astronomer at the Harvard-Smithsonian Center for Astrophysics (CfA), and lead author of a new paper in the Astrophysical Journal.

"They strengthen the case for an active galactic nucleus in the Milky Way's relatively recent past," he added.
Do they really need to strengthen the case for an active galactic nucleus in the Milky Way's past? Currently the galactic center is quiet, but there can be little doubt that it has not always been this way.

According to the spectroscopy data for 450 cool giant stars within one parsec from Sagittarius A, star formation in the galactic nucleus began to decline from its maximum ten billion years ago to its minimum a billion years ago, and started picking up again in the last few hundred million years. Roughly 80% of the stars formed more than five billion years ago. Therefore, it would seem logical than between ten and five billion years ago the Milky Way would have had a very active galactic nucleus.

Source: The star formation history of the Milky Way's Nuclear Star Cluster
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