Named to commemorate the centennial of the discovery of x-rays by the German physicist Wilhelm Conrad Roentgen {1845–1923} in November 1895. His first x-ray of a human being was of his wife’s hand. Roentgen’s research revolutionized medicine by providing a diagnostic tool still unrivaled in accuracy and simplicity. X-rays quickly became an indispensable part of patient care. Early in 1896 x-ray therapy came into being and has remained a standard treatment for cancer. This research has spread into many fields, especially astronomy, where x-rays provide a unique window on the universe. (M 27330) _ _.