Now two teams have pierced that veil with unprecedented clarity. One team used the Spitzer Space Telescope, which can see through dust, to chart the positions and orbital speeds of more than 110 million stars. They discovered a big surprise: Two of the galaxy’s four spiral arms are actually just small side-branches. On the other hand, the central bar of the galaxy turns out to be nearly twice as big as previously thought, Spitzer team member Robert Benjamin of the University of Wisconsin, Madison, said at a teleconference today.
Office of Strategic Communication