NASA's Spitzer Space Telescope has made the first measurements of the day and night temperatures of a planet outside our solar system. The infrared observatory revealed that the Jupiter-like gas giant planet circling very close to its sun is always as hot as fire on one side, and potentially as cold as ice on the other.

"This planet has a giant hot spot in the hemisphere that faces the star," said Dr. Joe Harrington of the University of Central Florida, Orlando, lead author of a paper appearing online today in Science. "The temperature difference between the day and night sides tells about how energy flows in the planet's atmosphere. Essentially, we're studying weather on an exotic planet."

The finding represents the first time any kind of variation has been seen across the surface of an extrasolar planet, a planet beyond our solar system.