When galaxies get close enough to each other, tidal forces can tug entire star systems out of place, distorting the shapes of the interacting pair in sometimes dramatic fashion. When galaxies with active galactic nuclei interact, the result can be spectacular, as in this Hubble Space Telescope view of Arp 282, made up of Seyfert galaxy NGC 169 (bottom) and IC 1559 (top). Hidden in the cores of both galaxies are supermassive black holes, actively feasting on surrounding stars, gas and dust. Delicate streams of matter can be seen visibly connecting the two galaxies in a dramatic, 3D-like demonstration of titanic tidal interactions.
Galaxy clusters are often described by superlatives. After all, they are huge conglomerations of galaxies, hot gas, and dark matter, representing the largest structures in the universe held together by gravity. New observations of the galaxy cluster SPT-CLJ2344-4243 (or Phoenix Cluster) at X-ray, ultraviolet, and optical wavelengths are helping astronomers better understand this extraordinary system.