ATLANTA (Reuters) - Stars heat planets: that's the astronomical rule. But a big gassy planet in the constellation Sagittarius is warming the star it orbits, just the opposite of what happens between Earth and the sun, scientists said on Wednesday. The hot spot on the star, known to astronomers as HD179949, might have been mistaken for a sun spot except that it is moving at the pace of the planet's orbit, rather than at the speed the star is rotating. "This is the first glimpse of a magnetic field on an extrasolar planet," Canadian researcher Evgenya Shkolnik of the University...