Galaxy NGC 4622, optical Hubble Space Telescope image. This spiral galaxy has two outer arms (blue stars) that spiral out in a clockwise direction. An inner arm (orange) spirals out in the opposite direction. This May 2001 observation, showed that the galaxy is rotating in a clockwise direction, the opposite direction to that expected by the orientation of the outer arms. Astronomers explain these opposing spiral arms by suggesting that this is the result of NGC 4622 colliding with a small companion galaxy. NGC 4622 lies about 111 million light years from Earth, in the constellation Centaurus.