Gamma rays from a dwarf galaxy solve an astronomical puzzle

A glowing blob known as “the cocoon”, which appears to be inside one of the enormous gamma-ray emanations from the center of our galaxy dubbed the “Fermi bubbles”, has puzzled astronomers since it was discovered in 2012.

In new research published in Nature Astronomy, we show the cocoon is caused by gamma rays emitted by fast-spinning extreme stars called “millisecond pulsars” located in the Sagittarius dwarf galaxy, which orbits the Milky Way. While our results clear up the mystery of the cocoon, they also cast a pall over attempts to search for dark matter in any gamma-ray glow it may emit.