A Little Windy

How to measure weather on a distant, volatile planet.  

Just more than a decade after discovering an extrasolar planet about 63 light-years away, scientists now have some insights into its turbulent atmosphere. HD 189733b, in the Vulpecula constellation, is known as a hot Jupiter, and it resides so close to its host star that it’s tidally locked—the same part of the surface always faces the star. Astronomers imaged its atmosphere as it passed in front of its star relative to Earth, which sent enough light back through the planet’s atmosphere to identify some atoms and molecules.

From there, researchers focused on sodium vapor to determine the wind speed in the planet’s atmosphere—they were able to detect related color shifts as the hot Jupiter passed its star, which indicates the atmosphere is moving. By measuring and carefully adjusting those readings, the researchers showed the winds were moving at a blistering 8,500 kilometers an hour.