CfA: Milky Way Had a Blowout 6 Million Years Ago

[bystander]

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

• arXiv.org > astro-ph > arXiv:1607.08364 > 28 Jul 2016

[alcor]

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

• arXiv.org > astro-ph > arXiv:1604.08210 > 14 Jul 2016

[Ann]

Click to view full size image

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

[neufer]

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

[Fred the Cat]

They are described as "bubbles" but how do we know they aren't ring-like? (Thankfully we have evidence for his existence too)

[alcor]

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.