Pair of colliding stars spill radioactive molecules into space. Astronomers have made the first definitive detection of a radioactive molecule in interstellar space: a form, or isotopologue of aluminum monofluoride (26AlF). The new data -- made with ALMA and the NOEMA radio telescopes -- reveal that this radioactive isotopologue was ejected into space by the collision of two stars, a tremendously rare cosmic event that was witnessed on Earth as a 'new star,' or nova, in the year 1670. Source 9y.