Our sun is travelling around the center of the Milky Way at 220 kilometers per second, says Gerry Gilmore with the Institute of Astronomy at the the University of Cambridge, referring to the fact that our Milky Way Galaxy lies inside a sphere, or “halo”, of dark matter that extends out far beyond the luminous Galactic disk, surrounded by a spheroidal halo of old stars and globular clusters, of which 90% lie within 100,000 light-years of the Galactic Center. “If there were no dark matter there, adds Gilmore, if there were just stars, we would be travelling at a ‘mere’ 150 km per second,” Gilmore adds.