The discovery of cometary x-rays
In 1996 scientists expressed surprise when they detected the first evidence that comets produce x-rays. They had no expectation that ice balls could do this. If you doubt the shock of this major discovery -- check out this report:
It took NASA several years to explain the phenomenon. But James McCanney had already offered an explanation even before the discovery was made. Indeed -- McCanney had predicted the discovery -- based on his plasma discharge comet model. McCanney actually contacted NASA and urged them to turn on their instruments during the passage of comet Hyakutake. But of course -- they ignored him.
The discovery was made by accident.
In 2000 NASA announced that the x-rays were produced by ions from the sun - and indeed this may be a partial explanation.
Notice -- the x-rays are produced on the sunward side of the comet --