X-Ray Image of the Perseus Galaxy Cluster (image) Johannes Gutenberg Universitaet Mainz Share Print E-Mail Caption This is an X-ray image of the Perseus galaxy cluster, approximately 240 million light-years away from Earth. The x-ray radiation emitted by galaxies and galaxy clusters still poses numerous puzzles to astrophysicists. In particular, it may provide clues to the nature of the mysterious dark matter. Credit NASA Usage Restrictions This image may only be used in connection with the press release "Cosmic x-rays may provide clues to the nature of dark matter", issued by Johannes Gutenberg University Mainz on February 8, 2018. Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.