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The Fermi bubbles are Milky-Way gamma-ray features that appear as two roughly-spherical shapes, each about 50,000 light years in diameter, extending into galactic halo from the center of the galactic disk, i.e., sitting on the Milky Way's axis. They were clearly observed by the Fermi Gamma-ray Space Telescope in 2010, after hints of them were had been seen in observations of earlier missions. Various theories regarding their precise mechanism and origin generally presume they are due to excitation of coronal gas in the galactic halo by some sort of energy from Sag A*, the Milky Way's supermassive black hole (SMBH).