Radiation from Jupiter

When they discuss the Galileo space craft, they are always talking ahout the immense radiation that Jupiter gives off.
Why does Jupiter give off radioation? How is it generated?

well, jupiter is pretty damn big, close to star mass (not too close, but lemme run with this). So it’s not too unlikely that fusion is going on, just not enough to be star-like.
However, as far as I know, this is still a mystery.

From The Nine Planets: