Astronomy Colloquium

RS Oph was observed in outburst on February 12, 2006 and, for at least the fifth time in recorded history, reached naked eye visibility. RS Oph is a member of a class of stars called recurrent novae because their outbursts have been detected more than once. We jumped at the opportunity to observe this system both with the large number of satellites now in orbit and ground based facilities that had far superior detectors to those available for its last outburst in January 1985. This system has a white dwarf (probably massive) in a 455 day orbit around a cool giant. The giant is transferring hydrogen rich matter onto the white dwarf at a rate that is sufficient for an explosion every 20 years or so. In contrast, a classical nova binary system also contains a white dwarf star but the mass losing star is a low mass star (like the sun) in a few hour orbit around the white dwarf and the time between explosions may be as long as 100,000 years or more. I will report on the unprecedented data that we obtained with X-ray satellites such as Chandra and Swift plus discuss the possible relationship between RS Oph and Supernovae of Type Ia. These latter explosions are thought responsible for the iron group elements in the Solar System and are now being used to study the evolution of the Universe.