Milky Way's 'Halo' Spins at Dizzying Speed

The cloud, called the Milky Way's halo, extends hundreds of thousands of light-years across. Using archived data from the European Space Agency's XMM-Newton telescope, astronomers found the halo is spinning in the same direction as the galaxy and almost as fast. "People just assumed that the disk of the Milky Way spins while this enormous reservoir of hot gas is stationary — but that is wrong.