Find out the latest thinking about our universe.
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bystander
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by bystander » Tue Aug 30, 2016 12:28 am
Milky Way Had a Blowout Bash 6 Million Years Ago
Harvard-Smithsonian Center for Astrophysics | 2016 Aug 29
[c][attachment=0]MilkyWayBlowout.jpg[/attachment][/c][hr][/hr]
The center of the Milky Way galaxy is currently a quiet place where a supermassive black hole slumbers, only occasionally slurping small sips of hydrogen gas. But it wasn't always this way. A new study shows that 6 million years ago, when the first human ancestors known as hominins walked the Earth, our galaxy's core blazed forth furiously. The evidence for this active phase came from a search for the galaxy's missing mass.
Measurements show that the Milky Way galaxy weighs about 1-2 trillion times as much as our Sun. About five-sixths of that is in the form of invisible and mysterious dark matter. The remaining one-sixth of our galaxy's heft, or 150-300 billion solar masses, is normal matter. However, if you count up all the stars, gas and dust we can see, you only find about 65 billion solar masses. The rest of the normal matter - stuff made of neutrons, protons, and electrons - seems to be missing. ...
The astronomers used the amount of absorption to calculate how much normal matter was there, and how it was distributed. They applied computer models but learned that they couldn't match the observations with a smooth, uniform distribution of gas. Instead, they found that there is a "bubble" in the center of our galaxy that extends two-thirds of the way to Earth. ...
The observations and associated computer models also show that the hot, million-degree gas can account for up to 130 billion solar masses of material. Thus, it just might explain where all of the galaxy's missing matter was hiding: it was too hot to be seen. ...
The Milky Way Hot Baryons and Their Peculiar Density Distribution: A Relic of Nuclear Activity - F. Nicastro
et al
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Attachments
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![MilkyWayBlowout.jpg (382.7 KiB) Viewed 563 times This artist's impression shows the Milky Way as it may have appeared 6 <br />million years ago during a "quasar" phase of activity. A wispy orange bubble <br />extends from the galactic center out to a radius of about 20,000 light-years. <br />Outside of that bubble, a pervasive "fog" of million-degree gas might account <br />for the galaxy's missing matter of 130 billion solar masses. <br />Credit: Mark A. Garlick/CfA](./download/file.php?id=25592&t=1&sid=a3caded97d8c9888f258c308c87083c7)
- This artist's impression shows the Milky Way as it may have appeared 6
million years ago during a "quasar" phase of activity. A wispy orange bubble
extends from the galactic center out to a radius of about 20,000 light-years.
Outside of that bubble, a pervasive "fog" of million-degree gas might account
for the galaxy's missing matter of 130 billion solar masses.
Credit: Mark A. Garlick/CfA
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk. — Garrison Keillor
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alcor
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by alcor » Wed Aug 31, 2016 3:59 pm
See also (which is linked in the press release)
A Distant Echo of Milky Way Central Activity closes the Galaxy's Baryon Census - F. Nicastro
et al
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Ann
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by Ann » Thu Sep 01, 2016 2:22 pm
From end to end, the newly discovered gamma-ray bubbles extend 50,000 light-years,
or roughly half of the Milky Way's diameter, as shown in this illustration.
Hints of the bubbles' edges were first observed in X-rays (blue) by ROSAT,
a Germany-led mission operating in the 1990s. The gamma rays mapped
by Fermi (magenta) extend much farther from the galaxy's plane.
Credits: NASA's Goddard Space Flight Center
Could these gamma-ray bubble's be related to the Milky Way blowout 6 million years ago?
Ann
Last edited by
Ann on Thu Sep 01, 2016 3:14 pm, edited 1 time in total.
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neufer
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by neufer » Thu Sep 01, 2016 3:06 pm
Ann wrote:
Could these gamma-ray bubble's be related to teh Milky Way's blowout 6 million years ago?
25,000 light years in 6 million years => average speed ~1250 km/sec.
- Why not
![Question :?:](./images/smilies/icon_question.gif)
Art Neuendorffer
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Fred the Cat
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by Fred the Cat » Thu Sep 01, 2016 6:43 pm
They are described as "bubbles" but how do we know they aren't
ring-like? (Thankfully we have evidence for his existence too)
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alcor
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by alcor » Mon Sep 05, 2016 1:55 am
You are not alone regarding a possible connection with the Fermi bubble. The authors of A Distant Echo of Milky Way Central Activity ..., in the second message above, make also this connection.