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Above, HD 189733b in front of its parent star. 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. (Credit: Mark A. Garlick/U. Warwick)


Wind whips across this exoplanet at 5,400 mph

Scientists have discovered winds of over 2 kilometers (1.24 miles) per second flowing around a planet outside of the Earth’s solar system.

The wind speed recorded is 20 times greater than the fastest ever known on Earth, where it would be seven times the speed of sound.

“This is the first ever weather map from outside of our solar system. Whilst we have previously known of wind on exoplanets, we have never before been able to directly measure and map a weather system,” says lead researcher Tom Louden of the University of Warwick’s astrophysics group.

The researchers measured the velocities on the two sides of exoplanet HD 189733b and found a strong wind moving at over 5,400 mph blowing from its dayside to its night side.

“HD 189733b’s velocity was measured using high resolution spectroscopy of the sodium absorption featured in its atmosphere. 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,” says Louden.

“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. 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.”

The researchers say that the techniques used could help the study of Earth-like planets.

[It takes stronger winds to move Titan’s dunes]

“We are tremendously excited to have found a way to map weather systems on distant planets,” says co-researcher Peter Wheatley. “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. ”

HD 189733b is one of the most studied of a class of planets known as “Hot Jupiters.” Over 10 percent larger than Jupiter, but 180 times closer to its star, HD 189733b has a temperature of 1,800º C (3,272º F).

Its size and relatively closeness to our solar system make it a popular target for astronomers. Past research has shown that the dayside of the planet would appear a bright shade of blue to the human eye, probably due to clouds of silicate particles high in its atmosphere.

The High Accuracy Radial Velocity Planet Searcher, in La Silla, Chile, collected the data. The Astronomical Journal Letters has accepted a paper on the findings.

Source: University of Warwick

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