They suspect they may be “the remnants from a burst of star formation or leftovers from an eruption by the supermassive black hole at our galaxy’s centre”, but they are still trying to confirm their origin.
Inside the bubbles, they say, “extremely energetic electrons of unknown origin interact with lower-energy light to generate the gamma rays that define these bubbles”. The image was created using data from the all-sky map made by NASA’s Fermi Gamma-Ray Space Telescope.
According to NASA, this is how they would appear to the naked eye if humans ‘could see gamma rays’. You know. Like, mutants. Or the Silver Surfer. [NASA]