The Milky Way's stars sprawl outwards in a series of concentric ripples, hinting that it might extend farther into space than was thought.
Data from the Sloan Digital Sky Survey confirm a previously known ring of stars at about 9,000 parsecs from the Sun. They also show another ring about 14,000 parsecs from the Sun, says a team led by Yan Xu of the National Astronomical Observatories of China in Beijing. These rings each form a ripple, making our Galaxy corrugated rather than flat.
The ripples may have formed when a dwarf galaxy passed through the Milky Way, creating rings of stars with its gravitational pull.