Comets, charge exchange, and a novel look at the X-ray universe

The discovery of cometary X-ray emission in 1996 with ROSAT has
revealed the importance of a fundamental process for the generation of
X-rays which was overlooked for a long time: charge exchange, a
process where X-rays are not produced by hot electrons, but by ions
picking up electrons from cold gas.  It has also provided a conceptual
breakthrough for the understanding of the soft X-ray background, and
has opened up entirely new fields of X-ray studies.  The talk will
attempt to put the various aspects of the study of charge exchange
reactions into a broader historical context, with special emphasis on
X-ray astrophysics, where cometary X-rays may have stimulated a novel
look at our universe.