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Webb predicts the weather forecast on exoplanet WASP-43 b

An international team of researchers has harnessed the power of NASA’s James Webb Space Telescope to unravel the mysteries of distant worlds. The telescope’s precise measurements and advanced capabilities have allowed scientists to map the weather on WASP-43 b, a hot gas-giant exoplanet located trillions of miles away.

The study, published in Nature Astronomy, was led by Taylor Bell, a researcher from the Bay Area Environmental Research Institute.

The team’s findings suggest the presence of thick, high clouds on the planet’s nightside, clear skies on the dayside, and powerful equatorial winds that mix atmospheric gases at speeds of up to 5,000 miles per hour.

WASP-43 b is a planet of extremes

WASP-43 b, discovered in 2011, is a “hot Jupiter” type of exoplanet. Similar in size to Jupiter and composed primarily of hydrogen and helium, this world orbits its star at an incredibly close distance of just 1.3 million miles.

As a result, the planet is tidally locked, with one side perpetually facing the star and the other shrouded in eternal darkness.

“With Hubble, we could clearly see that there is water vapor on the dayside. Both Hubble and Spitzer suggested there might be clouds on the nightside,” explained Taylor Bell.

“But we needed more precise measurements from Webb to really begin mapping the temperature, cloud cover, winds, and more detailed atmospheric composition all the way around the planet,” Bell continued.

Mapping temperature and inferring weather patterns

By employing phase curve spectroscopy, the researchers measured tiny changes in the brightness of the star-planet system as WASP-43 b completed its 19.5-hour orbit.

Using Webb’s Mid-Infrared Instrument (MIRI), the team collected light measurements every 10 seconds for more than 24 hours, enabling them to calculate the temperature of different sides of the planet as they rotated into view.

The measurements revealed a stark contrast between the planet’s dayside and nightside temperatures. The dayside, with an average temperature of nearly 2,300 degrees Fahrenheit (1,250 degrees Celsius), is hot enough to forge iron.

In comparison, the nightside is significantly cooler at 1,100 degrees Fahrenheit (600 degrees Celsius). The data also helped locate the planet’s hottest spot, which is slightly shifted eastward due to supersonic winds that move heated air in that direction.

“The fact that we can map temperature in this way is a real testament to Webb’s sensitivity and stability,” remarked Michael Roman, a co-author from the University of Leicester in the U.K.

Missing methane and high-speed winds on WASP-43 b

The broad spectrum of mid-infrared light captured by Webb also allowed the researchers to measure the abundance of water vapor (H2O) and methane (CH4) in the planet’s atmosphere.

While water vapor was detected on both the dayside and nightside, the data revealed a surprising absence of methane.

“The fact that we don’t see methane tells us that WASP-43 b 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.

“If winds move gas around from the dayside to the nightside and back again fast enough, there isn’t enough time for the expected chemical reactions to produce detectable amounts of methane on the nightside,” she concluded.

The team believes that this wind-driven mixing results in a uniform atmospheric chemistry throughout the planet, a finding that was not apparent from previous observations using the Hubble and Spitzer space telescopes.

New era of exoplanet science

The James Webb Space Telescope has opened a new frontier in exoplanet science, enabling researchers to map the weather patterns and atmospheric composition of distant worlds like never before.

By revealing the extreme temperature variations, thick clouds, and supersonic winds on WASP-43 b, this study demonstrates the telescope’s extraordinary capabilities and sets the stage for a new era of exploration.

As scientists continue to leverage Webb’s advanced instruments and precise measurements, they will undoubtedly uncover more fascinating insights into the diverse and captivating worlds that populate our universe, bringing us closer to understanding the complexity and potential habitability of planets beyond our solar system.

The full study was published in the journal Nature Astronomy.


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