My 2-year-old son, Benjamin, is already learning the planets at school. He came home the other day and informed me that Saturn has rings, Jupiter has a red spot, and Neptune is very, very windy. It was the last point that struck me. It's true, Neptune has some of the highest wind speeds in the solar system (more than 1,200 miles per hour at some latitudes). But I realized I had no idea why Neptune was "very, very windy."


Voyager 2 imaged Neptune when it flew by in 1989. Methane gas, which preferentially absorbs red light, causes the blue hue. The dark spot in the middle is a cyclonic storm as wide as Earth.

Courtesy NASA/JPL.

Fortunately, I wasn't the only one curious about it, and research published this week in the journal Astronomy and Astrophysics addresses that very question. Glenn Orton (NASA/Jet Propulsion Laboratory) used the European Southern Observatory's Very Large Telescope facility in Chile to take Neptune's temperature.

Orton and his team find that Neptune's south pole is some 18°F (10° Celsius) warmer than the rest of the planet. In a press release issued by NASA, Orton attributes the difference to a seasonal effect — a year on Neptune is about 165 Earth years long, and it's been summer in the southern hemisphere for the past four decades. Even though Neptune is "very, very far away" (another tidbit I learned from my boy), all that extra sunlight hitting one side of the planet eventually adds up. This extra daylight causes the temperature difference and most likely plays a factor in the global winds.

If Orton is right, the north pole should become warm in about 80 years. I won't be here to report on it, but maybe Benjamin will have something to say when the time comes.


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