Astronomers examining the distribution of stars in the Milky Way have found them to be imbalanced, and suggest that this offset is due to the “ripples” of collision or close encounters with other galaxies within the past 100 million years. All things being equal, the stars in the galaxy ought to be evenly distributed above and below the galactic plane. Instead, a recent distance survey of 300,000 stars carried out with the Sloan Digital Sky Survey reveal that the distribution is off of center, which would be expected if the galaxy had encountered a gravitational disturbance. Long after the approaching galaxy has either passed by or been absorbed into the Milky Way, the ripples of that encounter would still be working their way through the Milky Way’s stars, giving the distribution we see today. Read more here from Astronomy Now.