Gamma rays radiate from the Milky Way's center, but where do they come from?
Scientists have discovered gigantic structures 25,000 light-years tall ballooning above and below the Milky Way. Within each curved lobe, extremely energetic electrons of unknown origin interact with lower-energy light to generate the gamma rays that define these bubbles. The galactic-scale structures could be remnants from a burst of star formation or leftovers from an eruption by the supermassive black hole at our galaxy's center. Scientists aren't sure yet, but the more they learn about this amazing structure, which may be only a few million years old, the better we'll understand the Milky Way. While not immediately visible to NASA's Fermi Gamma-ray Space Telescope, these unexpected features were brought into sharp relief by a group of scientists who processed data from Fermi's all-sky map. The visualization below shows how artists imagine the lobes would appear if gamma rays were visible to the naked eye.