Space meteorologists: Cloudy, with a chance of 8,600 kph winds?

For the first time, scientists have measured wind speeds on a planet outside the Earth’s solar system.

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 5400mph from the heated day side to the night side. The day side of the planet appears blue due to scattering of light from silicate haze in the atmosphere. The night side of the planet glows a deep red due to its high temperature.

The forecast is in from beyond Earth’s solar system – and the weather is blustery out there.  

Researchers from the University of Warwick have measured wind speeds of more than 8,600 kilometers per hour (5,400 miles per hour) in the atmosphere of an exoplanet 60 light years away, according to a study published last week in the Astrophysics Journal Letters.

The figures – 20 times faster than the fastest speeds ever recorded on Earth, and seven times swifter than the speed of sound – represent the first time scientists have measured and mapped weather phenomena on a planet outside the solar system. The technique, the researchers say, could further studies of weather conditions on Earth-like planets.

“We are tremendously excited to have found a way to map weather systems on distant planets,” said Peter Wheatley of the University of Warwick’s Astrophysics Group in a statement. “As we develop the technique further we will be able to study wind flows in increasing detail and make weather maps of smaller planets. Ultimately this technique will allow us to image the weather systems on Earth-like planets.”

To measure wind speed, the scientists took advantage of the Doppler effect in their observation of the host star’s light as it was absorbed by molecules in the atmosphere of exoplanet HD 189733b. As the planet rotated towards and away from Earth, they measured subtle changes in the wavelengths of light striking its atmosphere.

The scientists then used those shifts to calculate wind speeds.

“The surface of the star is brighter at the centre 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,” lead researcher Tom Louden said in a statement. “For the first time we’ve used this information to measure the velocities on opposite sides of the planet independently, which gives us our velocity map.”

It helped that HD 189733b belonged to a class of cosmic bodies called “hot Jupiters” – gas giants that closely orbit their host stars. More than 10 percent larger than Jupiter and about 180 times closer to its star, HD 189733b is an ideal target for astronomers looking to study and observe exoplanets.

The data was collected by the High Accuracy Radial Velocity Planet Searcher, a high-precision spectrograph installed on the European Southern Observatory’s telescope in La Silla, Chile.

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