Bullet Cluster
Energetic X-rays (pink) are emitted by hot normal matter that has piled up where two clusters of galaxies have collided. The dark matter (blue) has mysteriously passed through the crash undisturbed.
Credit:X-ray: NASA/CXC/CfA/M.Markevitch et al.; Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al.; Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/D.Clowe et al.
