Measurements of unprecedented detail returned by Japan's Hitomi satellite have allowed scientists to track the motion of X-ray-emitting gas at the heart of the Perseus cluster of galaxies for the first time. The results showcase the premiere of a next-generation X-ray instrument whose key components were developed at NASA's Goddard Space Flight Center. Led by the Japan Aerospace Exploration Agency (JAXA), Hitomi was launched on February 17. Hitomi was able to peer into the Perseus cluster of galaxies, an assemblage of thousands of galaxies bound together by gravity. Located about 240 million light-years away and named for its host constellation, the Perseus galaxy cluster contains a vast amount of extremely hot gas. At temperatures averaging 90 million degrees Fahrenheit, the gas glows brightly in X-rays. Prior to Hitomi's launch, astronomers lacked the capability to measure the detailed dynamics of this gas. For the first time, thanks to Hitomi's revolutionary Soft X-ray Spectrometer (SXS), astronomers have mapped the motion of X-ray-emitting gas in a cluster of galaxies and shown it moves at cosmically modest speeds.