Unexpected X-Rays from Perseus Galaxy Cluster

Explanation: Why does the Perseus galaxy cluster shine so strangely in one specific color of X-rays? No one is sure, but a much-debated hypothesis holds that these X-rays are a clue to the long-sought identity of dark matter . At the center of this mystery is a 3.5 Kilo- electronvolt (KeV) X-ray color that appears to glow excessively only when regions well outside the cluster center are observed, whereas the area directly surrounding a likely central supermassive black hole is actually deficient in 3.5 keV X-rays. One proposed resolution -- quite controversial -- is that something never seen before might be present: fluorescent dark matter (FDM). This form of particle dark matter might be able to absorb 3.5 keV X-radiation. If operating, FDM , after absorption, might later emit these X-rays from all over the cluster, creating an emission line . However, when seen superposed in front of the central region surrounding the black hole , FDM's absorption would be more prominent, creating an absorption line . Pictured , a composite image of the Perseus galaxy cluster shows visible and radio light in red, and X-ray light from the Earth-orbiting Chandra Observatory in blue.

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