NASA Kepler: Big weather on hot Jupiters

This exoplanet weather map shows temperatures on a hot Jupiter known as "HAT-P-2b". 

Among the hundreds of new planets discovered by NASA's Kepler spacecraft are a class of exotic worlds known as "hot Jupiters." 

Unlike the giant planets of our own solar system, which remain at a safe distance from the sun, these worlds are reckless visitors to their parent stars.

They speed around in orbits a fraction the size of Mercury's, blasted on just one-side by starlight hundreds of times more intense than the gentle heating experienced by Jupiter here at home."

Meteorologists watching this video are probably wondering what kind of weather a world like that might have.

Heather Knutson

The short answer is "big." Heather Knutson of Caltech made the first weather map of a hot Jupiter in 2007. "It's not as simple as taking a picture and—voila!—we see the weather," says Knutson.

These planets are hundreds of light years from Earth and they are nearly overwhelmed by the glare of their parent stars.

"Even to see the planet as a single pixel next to the star would be a huge accomplishment." Instead, Knutson and colleagues use a trick dreamed up by Nick Cowan of Northwestern University.

The key, she explains, is that "most hot Jupiters are tidally locked to their stars. This means they have a permanent dayside and a permanent night side.

Nick Cowan

As we watch them orbit from our vantage point on Earth, the planets exhibit phases—e.g., crescent, gibbous and full.

By measuring the infrared brightness of the planet as a function of its phase, we can make a rudimentary map of temperature vs. longitude."

NASA's Spitzer Space Telescope is the only infrared observatory with the sensitivity to do this work.

Since Knutson kick-started the research in 2007, nearly a dozen hot Jupiters have been mapped by astronomers using Spitzer.

Nikole Lewis

The most recent study, led by Nikole Lewis, a NASA Sagan Exoplanet Fellow working at MIT, shows a gas giant named HAT-P-2b.

"We can see daytime temperatures as high as 2400 K," says Lewis, "while the nightside drops below 1200K. Even at night," she marvels, "this planet is ten times hotter than Jupiter."

These exoplanet maps may seem crude compared to what we're accustomed to on Earth, but they are a fantastic accomplishment considering that the planets are trillions of miles away.