Bernd Aschenbach, Hermann-Michael Hahn and Joachim Trumper
Invisible Sky: Rosat and the Age of X-Ray Astronomy (Hardback) [Bernd Aschenbach, Hermann-Michael Hahn and Joachim Trumper - 1998]
175 pgs, 1998 Springer/Verlag ISBN 978-0387949284
Astronomy is not confined to the visible sky. Since the 1950's, technology has helped scientists, particularly astronomers, see previously invisible aspects of the solar system.