... Many believe that the Hubble Space Telescope's recent distance measurement to this galaxy accurately calibrates the expansion rate of the universe. ... Pictured is M31's companion galaxy M32. ... The Proportional Counter Array (PCA) and the High Energy X-ray Timing Experiment (HEXTE) will provide the best timing information in the widest X-ray energy range yet available. ... Just like our own Milky Way Galaxy, the nearest major galaxy M31 has many star systems spewing high energy radiation. ...