A surprising new class of X-ray pulsating variable stars has been discovered by a team of Villanova University astronomers. New X-ray observations obtained by NASA's Chandra X-ray Observatory reveal that the star known as "d Cephei," the bright prototype of all Classical Cepheids, is actually a periodic pulsed X-ray source. At a distance of 890 light years away, this star, after which all Cepheids are named, is also one of the closest. Cepheids are among the most astronomically important objects in the Universe, for by measuring the pulsation periods and brightness of Cepheids, astronomers can measure distances to other galaxies.