Webb maps weather on hot gas-giant exoplanet 280 light-years away

Using NASA's James Webb Space Telescope (JWST), researchers have mapped the weather on WASP-43 b - a Jupiter-sized gas giant exoplanet roughly 280 light-years away, in the constellation Sextans, thanks to the telescope's extraordinary ability to measure temperature variations and detect atmospheric gases trillions of miles away.

WASP-43 b was discovered in 2011 and has been observed with numerous telescopes, including NASA's Hubble and now-retired Spitzer space telescopes.

Precise brightness measurements from Webb, combined with 3D climate models and past observations from other telescopes, suggest the presence of thick, high clouds covering the nightside, clear skies on the dayside, and equatorial winds upwards of 5,000 miles per hour mixing atmospheric gases around the hot planet.

To map the weather on WASP-43 b, researchers used a technique called phase curve spectroscopy that involves measuring tiny changes in the brightness of the star-planet system as the planet orbits its star. Webb's Mid-Infrared Instrument  (MIRI) measured light from the WAS43 system every 10 seconds for more than 24 hours.

The measurements revealed that the dayside of the planet has an average temperature of nearly 2,300 degrees Fahrenheit (1,250 degrees Celsius) whereas the nightside is significantly cooler at 1,100 degrees Fahrenheit (600 degrees Celsius).

In addition, the analysis suggested that the nightside is probably covered in a thick, high layer of clouds that prevent some of the infrared light from escaping to space. As a result, the nightside - while very hot - looks dimmer and cooler than it would if there were no clouds.

The researchers were also able to measure the amount of water vapor (H2O) and methane (CH4) around the planet, thanks to the broad spectrum of mid-infrared light captured by Webb. 

The spectra show clear signs of water vapor on the nightside and the dayside as well, providing additional information about how thick the clouds are and how high they extend in the atmosphere. Surprisingly, the data also shows a distinct lack of methane anywhere in the atmosphere. While methane cannot exist on the hot dayside due to its high temperature, it should be detectable on the cooler nightside where it can be stable. 

"The fact that we don't see methane tells us that WASP-43b must have wind speeds reaching something like 5,000 miles per hour," explained Joanna Barstow, a co-author from the Open University in the U.K.

This study was led by Taylor Bell, a researcher from the Bay Area Environmental Research Institute. 

Spotted: @NASAWebb unveiled the weather patterns on a hot gas-giant exoplanet 280 light-years away.Discover how researchers are able to map temperature and infer the weather: https://t.co/XQ6dgmSQe4 pic.twitter.com/WmQs0WaqXN

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