While looking at the galaxy cluster Abell 2667, astronomers found an odd-looking spiral galaxy (shown here in the upper left hand corner of the image) that ploughs through the cluster after being accelerated to at least 3.5 million km/h by the enormous combined gravity of the cluster's dark matter, hot gas and hundreds of galaxies.

Credit: NASA, ESA, Jean-Paul Kneib (Laboratoire d'Astrophysique de Marseille)