How did this exoplanet get 5,400 mph winds?

Scientists have recorded wind speeds seven times the speed of sound hurtling around exoplanet HD 189733b.

Courtesy of Mark A. Garlick/University of Warwick
The planet HD 189733b is shown here in front of its parent star. A belt of wind around the equator of the planet travels at 5,400 mph from the heated day side to the cooler night side, researchers say.

Violent winds can cause chaos on Earth, but even hurricanes are dwarfed by the blasts of air discovered on exoplanet HD 189733b.

Scientists have clocked wind speeds over 5,400 mph hurtling around this planet, astronomers say. That’s 20 times faster than the highest wind speeds recorded on Earth.

"This is the first ever weather map from outside of our solar system," said lead researcher Tom Louden, an astrophysicist at the University of Warwick. "Whilst we have previously known of wind on exoplanets, we have never before been able to directly measure and map a weather system.”

Warwick astronomers used HARPS, the High Accuracy Radial velocity Planet Searcher in La Silla, Chile, to watch the planet, located far outside of Earth’s solar system, as it passed in front of its host star.

"The surface of the star is brighter at the center than it is at the edge, so as the planet moves in front of the star the relative amount of light blocked by different parts of the atmosphere changes," explained Dr. Louden in a press release.

The researchers detected the speed by looking at wavelengths for atmospheric sodium, said Louden. "As parts of HD 189733b’s atmosphere move towards or away from the Earth, the Doppler effect changes the wavelength of this feature, which allows the velocity to be measured."

They determined that the incredible winds blow from the exoplanet's day side to its night side.

The fastest wind gust ever recorded on Earth was in 1996 during Tropical Cyclone Olivia, when weather measured wind speeds of 253 mph.

The exoplanet's 5,000 mph gusts are caused by its proximity to its star, according to the researchers.

HD 189733b is nearly 63 light years from our solar system, and is one of a bizarre class of planets called "Hot Jupiters."

In 2007, NASA's Spitzer Space Telescope measured the heat from the planet. They found that its atmosphere reaches almost 3,700 degrees Fahrenheit on the day side, but is more than 500 degrees cooler on the night side.

This extreme temperature shift, the scientists concluded, should cause fierce winds to roar from the day side to the night side.

All wind, even here on Earth, is driven by temperature differences. Simply put, heat makes air molecules expand and rise, leaving a low-pressure area behind. When cooler air rushes from a high-pressure area to fill in the low-pressure area, we call that movement "wind." 

The researchers at Warwick say that the Doppler technique that they used to map wind speeds on this exoplanet could be useful on other planets, as well.

"As we develop the technique further, we will be able to study wind flows in increasing detail and make weather maps of smaller planets," said co-author Peter Wheatley in the release. "Ultimately this technique will allow us to image the weather systems on Earth-like planets."

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