<p>Two spiral <a href="http://science.nationalgeographic.com/science/space/universe/galaxies-article/">galaxies</a> in the Canis Major constellation collide in an encounter fraught with supernovae and incredibly bright x-rays.</p><p>X-ray binary systems—consisting of one star orbiting a neutron star or black hole—give off these luminous x-rays. The spiral galaxies NGC 2207 and IC 2163 contain one of the largest collections of such systems. (Learn <a href="http://voices.nationalgeographic.com/2014/09/26/astronomers-clue-in-to-why-binary-stars-are-so-bountiful/">why binary stars are so prevalent</a>.)</p><p dir="ltr">Researchers believe these superbright x-rays could be evidence of an as-yet-undiscovered intermediate size of black hole. (Read about <a href="http://ngm.nationalgeographic.com/2014/03/black-holes/finkel-text">black holes</a> in <em>National Geographic</em> magazine.)</p><p dir="ltr">The composite image above is a combination of views, with x-rays in pink; visible light in blue, white, orange, and brown; and infrared light in red.</p><p dir="ltr"><em>—By Jane J. Lee, photo gallery by Mallory Benedict</em></p>