In 2010 astrophysicists found a pair of, well, blobs hovering above and below the plane of our Milky Way galaxy. The blobs are huge—30,000 light-years tall—and glowing with gamma rays. Researchers called them Fermi bubbles, after the Fermi space telescope that spotted them. But what on Earth—I mean, what in the Milky Way—could produce them?

Physicists have a few ideas. The Fermi bubbles could be powered by the black hole at the center of our galaxy. As the black hole devours nearby stars, some in-falling matter escapes as hot plasma. If the black hole eats a star every 30,000 years, that hot plasma could provide enough energy to power the gamma-ray bubbles. So says a study in Astrophysical Journal Letters. [K.-S. Cheng et al, Origin of the Fermi Bubble]

But what if the bubbles came not from the black hole's steady exhalation, but from a relatively recent black hole belch? A study at arXiv.org ventures that the Milky Way's black hole may have flared up one or two million years ago, sending off powerful jets of energetic particles. [Fulai Guo and William Mathews, Fermi Bubbles: Evidence for a Possible Recent AGN Jet Activity in the Galaxy]

Astronomers see such jets in other galaxies. If it happened here, it could explain why the Milky Way has been accessorizing.

—John Matson

[The above text is an exact transcript of this podcast]