"It turns out that there are a significant number of asteroids that aren't just a single object, but two and even on occasion three in orbit around one another," Pollock said. He and his colleagues record information related to changes in amount of light reflected from asteroids. Sometimes this indicates the existence of a pair of asteroids that are revolving around each other... "When a single, irregularly shaped asteroid spins, the amount of reflective area changes and it appears to change brightness," Pollock said. "When you have two rotating asteroids revolving around one another, the brightness changes are much more...