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Strange weather on 'hot Jupiters' explained

Though scientists have yet to find alien life on distant exoplanets, much about those planets certainly seems alien — especially the weather.
Image: HD 189733b
An artist's impression of HD 189733b and its star.
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Though scientists have yet to find alien life on distant exoplanets, much about those planets certainly seems alien — especially the weather.

Now researchers have developed a model that can explain some of the bizarre weather patterns seen on other worlds.

Many of the roughly 300 extrasolar planets discovered so far are called "hot Jupiters" because they are large gas giants like our own Jupiter. Often, these planets orbit much closer to their stars than Jupiter does to the sun, so their daylight temperatures can reach 3,000 degrees Fahrenheit (1,600 degrees Celsius)— much hotter than any planet in our solar system.

While many extrasolar planets are too far away to detect anything at all about their weather, for a few planets scientists have been able to infer temperature changes from the varying brightness of the planet as it rotates relative to the Earth.

On one such planet, called HD 189733b, Spitzer Space Telescope observations showed the night-side temperature exceeds 1,300 Fahrenheit, which is much warmer than scientists expected.

Because many exoplanets orbit so close in to their stars, scientists think they are often "tidally locked," or trapped in position with one side permanently facing the star's light and the other side in perpetual nighttime. Somehow, heat gets transported from the daytime to the nighttime side of the planets, though how this happens has not been understood.

Now a new model created by Adam Showman of the University of Arizona and his team finally explains the processes creating the exotic weather patterns seen on exoplanets.

"Our model I think is the most realistic in the sense that it includes not only the weather processes in the atmosphere but couples them to how heat is absorbed and lost," Showman told "We created a pretty good representation that matches the observations."

The researchers found that fast-moving jet streams could carry warm air from the sunny side to the dark side of a planet. To account for the temperatures measured on planets such as HD 189733b, these streams would have to be speeding along at 7,000 mph(11,000 kph).

"You're talking about winds fast enough to carry you in a hot air balloon from San Francisco to New York in 25 minutes," Showman said.

While jet streams occur on planets in our solar system, including Jupiter and Earth, the streams are generally smaller and slower-moving than what's not being suggested for exoplanets.

"The basic chemical and physical processes are similar, but all the details are different," Showman said. "These planets are so close to their stars, so their temperatures are much higher and winds speeds are much higher. These types of jet streams are something that doesn't exist in our solar system."

While the strange weather patterns on some exoplanets would certainly be fascinating to see up close, they wouldn't be very hospitable to life like us.

"Hot Jupiters are pretty crazy places," Showman said.  "Expect supersonic winds and dayside temperatures hot enough to melt lead and rocks. Only problem is, if you tried to visit, you'd be fried to a crisp before you could enjoy the view."