R Aquarii is a pair of a) a white dwarf star that steadily burns at a relatively cool temperature and b) a highly variable red giant. As they orbit each other, the white dwarf pulls material from the red giant onto its surface. Over time, enough of this material accumulates and triggers an explosion. Astronomers have seen such outbursts over recent decades. Evidence for much older outbursts is seen in the spectacular structures observed by NASA’s Hubble Space Telescope (red and blue). X-ray data from Chandra (purple) shows how a jet from the white dwarf is striking material surrounding it and creating shock waves, similar to sonic booms from supersonic planes. (source: chandra.harvard.edu)