Big weather on hot Jupiters

May 27, 2013 by Dr. Tony Phillips
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. The short answer is "big."

Heather Knutson of Caltech made the first 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. As we watch them 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 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.

The most recent study, led by Nikole Lewis, a NASA Sagan Fellow working at MIT, shows a named HAT-P-2b. "We can see 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.

The maps show huge day-night temperature differences typically exceeding 1000 degrees. Researchers believe these thermal gradients drive ferocious winds blowing thousands of miles per hour.

Without regular pictures, researchers can't say what this kind of windy weather looks like. Nevertheless, Knutson is willing to speculate using climate models of Jupiter as a guide.

"Weather on hot Jupiters," she predicts, "is really big."

Over the years, planetary scientists have developed computer models to reproduce the storms and cloud belts in Jupiter's atmosphere. If you take those models and turn up the heat, and slow down the rotation to match the tidally-locked spin of a hot Jupiter, weather patterns become super-sized. For instance, on a hot Jupiter the Great Red Spot might grow as large as a quarter the size of the planet and manifest itself in both the northern and southern hemispheres.

"Just imagine what that would look like—a pair of giant eyes staring out into space!" says Lewis.

Meanwhile, Jupiter's famous belts would widen so much that only two or three would fit across the planet's girth.

Ordinary clouds of water and methane couldn't form in such a hot environment. Instead, Knutson speculates that hot Jupiters might have clouds made of silicate—that is, "rock clouds."

"Silicates are predicted to condense in such an environment," she says. "We're already getting some hints that clouds might be common on these planets, but we don't yet know if they're made of rock."

For now just one thing is certain: The meteorology of is out of this world.

Explore further: Spitzer telescope puts planets in a petri dish

Related Stories

Spitzer telescope puts planets in a petri dish

May 06, 2013

(Phys.org) —Our galaxy is teeming with a wild variety of planets. In addition to our solar system's eight near-and-dear planets, there are more than 800 so-called exoplanets known to circle stars beyond ...

Highly inflated Jupiters

Dec 10, 2012

There are currently 851 confirmed extra-solar planets. Of these, 289 were detected because their orbits (as seen from Earth) take them across the face of their host star, dimming the star's light in a transit ...

Recommended for you

Quest for extraterrestrial life not over, experts say

Apr 18, 2014

The discovery of an Earth-sized planet in the "habitable" zone of a distant star, though exciting, is still a long way from pointing to the existence of extraterrestrial life, experts said Friday. ...

Continents may be a key feature of Super-Earths

Apr 18, 2014

Huge Earth-like planets that have both continents and oceans may be better at harboring extraterrestrial life than those that are water-only worlds. A new study gives hope for the possibility that many super-Earth ...

Exoplanets soon to gleam in the eye of NESSI

Apr 18, 2014

(Phys.org) —The New Mexico Exoplanet Spectroscopic Survey Instrument (NESSI) will soon get its first "taste" of exoplanets, helping astronomers decipher their chemical composition. Exoplanets are planets ...

User comments : 0

More news stories

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Cosmologists weigh cosmic filaments and voids

(Phys.org) —Cosmologists have established that much of the stuff of the universe is made of dark matter, a mysterious, invisible substance that can't be directly detected but which exerts a gravitational ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.