Astronomers have finally identified the source of unusual X-rays coming from the bright star gamma-Cas. The culprit is an unseen companion star that is pulling in material from its larger neighbor. This discovery brings an end to a mystery that has puzzled scientists for more than fifty years. New high-resolution data from the X-Ray Imaging and Spectroscopy Mission (XRISM) showed that the X-rays are tied to the orbit of a nearby white dwarf star. By tracking this motion, researchers were able to confirm the true origin of the emissions. The findings are described in a study led by Yaël Nazé of the University of Liège, Belgium. "There has been an intense effort to solve the mystery of gamma-Cas across many research groups for many decades. And now, thanks to the high-precision observations of XRISM, we have finally done it," says Yaël.…