Exoplanet HD 189733b is an extremely windy place, according to researchers, who say it is the first time weather on an exoplanet has been observed.
Writing in the Astrophysical Journal Letters, researchers from the University of Warwick say winds on the planet, which is over 60 light years away, blow at an astonishing 8,690 kilometers per hour from its day side to the night side. That is 20 times faster than the most severe wind ever measured on Earth.
“This is the first ever weather map from outside of our solar system,” said Tom Louden, of the University of Warwick’s Astrophysics group. “Whilst we have previously known of wind on exoplanets, we have never before been able to directly measure and map a weather system.”
The exoplanet has been widely studied and is considered a “Hot Jupiter” type of planet, meaning it is about 10 percent larger than Jupiter, but is 180 times closer to its star. The temperature on HD 189733b can reach 1,200 Celsius, researchers said.
Louden said the measurements were made using “high resolution spectroscopy of the sodium absorption featured in its atmosphere,” adding that as parts of the atmosphere move either toward or away from Earth, the Doppler effect of the sodium wavelength can be measured. That, in turn, can be used to measure wind velocity.
“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,” he said. “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 said their technique could be used to map weather on other exoplanets.