Astronomers say that nothing similar has ever been seen before.
The astronomers, from the Joint Astronomy Centre in Hawaii, were mapping the magnetic structure of galaxy M82 in order to see stars being born in smouldering gas clouds. This is a new feature of galaxies that we didn't know about before and could show how magnetic fields help shape the evolution of starburst regions. The most likely explanation for the bubble is that enormously energetic winds are forcing the magnetic field into the outer halo of the galaxy. The winds are outflows of interstellar gas, powered by stars. Galaxy M82 makes up to fifty times more stars than other galaxies, but the reason for this remains unexplained.