Fermi bubbles

What made the giant gamma-ray lobes above and below the Milky Way’s center, and which fast particles keep them glowing?[1]

Two enormous lobes of gamma rays rise above and below the Milky Way’s center. What powered them, and which particles make them shine? Fast protons can strike surrounding gas and create particles that decay into gamma rays. Fast electrons can instead transfer energy to existing light through inverse Compton scattering. These different routes can fit the radiation yet imply different particle energies, cooling times and formation histories.[1] [2]

Gamma rays alone allow competing explanations. A current preprint reports associated neutrinos, while the complete formation history remains model dependent.[2] [3]

Both proton and electron models fit the June 2026 gamma-ray analysis. In proton models the required energy depends on the assumed gas density; electrons lose energy quickly, requiring sufficiently rapid transport or renewed acceleration. The September-revised neutrino preprint reports an association interpreted as energetic ions. It is an outside team’s analysis of IceCube data, not a collaboration discovery statement or a unique account of the central energy source.[2] [3]

They preserve clues to powerful activity in the center of our own galaxy.[1]

Emission mechanisms change inferred energies and timescales, so they affect whether star formation or black-hole activity can supply the required power.[1] [2]