NASA’s Webb Maps Weather on WASP-43 b

wasp-43 b artistic concept

The universe continues to unveil its secrets, and NASA's James Webb Space Telescope (JWST) is at the forefront of this revolution. Recently, an international team of researchers mapped the weather on the distant exoplanet WASP-43 b, located 280 light-years away. Using precise brightness measurements and advanced 3D climate models, they have uncovered extraordinary details about this hot gas giant's atmospheric conditions, including thick clouds, clear skies, and rapid equatorial winds.

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Discovering WASP-43 b: A Hot Jupiter Exoplanet

What is WASP-43 b?

WASP-43 b is a "hot Jupiter," a gas giant similar in size to Jupiter but much hotter. It orbits its star at a mere 1.3 million miles, causing extreme temperatures and unique atmospheric conditions. This close orbit, completed in just 19.5 hours, results in the planet being tidally locked, with one side facing the star continuously while the other remains in darkness.

Tidally Locked Giant

The term "tidally locked" means that the planet's rotational period matches its orbit around the star, much like how our Moon always shows the same face to Earth. This leads to one hemisphere constantly bathed in starlight while the other remains perpetually dark.

Leveraging the James Webb Space Telescope's Capabilities

WASP-43 b: Mid-Infrared Observations with JWST

Researchers utilized JWST’s Mid-Infrared Instrument (MIRI) to measure light variations from the WASP-43 system every 10 seconds over a 24-hour period, creating a comprehensive temperature map across the planet.

Supersonic Winds and Dramatic Temperature Differences on WASP-43 b

On the star-facing dayside, temperatures soar to nearly 2,300 degrees Fahrenheit (1,250 degrees Celsius), while the nightside cools down to 1,100 degrees Fahrenheit (600 degrees Celsius). These temperature shifts are driven by supersonic winds exceeding 5,000 miles per hour, redistributing heat and causing a notable eastward shift of the planet's hottest spot.

This set of maps illustrates the temperature of the hot gas-giant exoplanet WASP-43 b's visible side as it orbits its star. The dayside of the planet becomes visible just before and after it passes behind the star. These temperatures were determined from over 8,000 brightness measurements of 5- to 12-micron mid-infrared light detected by the Mid-Infrared Instrument (MIRI) on NASA’s James Webb Space Telescope. Generally, hotter objects emit more mid-infrared light.

wasp-43 b temperatures
Credits: Science: Taylor J. Bell (BAERI); Joanna Barstow (Open University); Michael Roman (University of Leicester) Graphic Design: NASA, ESA, CSA, Ralf Crawford (STScI)

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Atmospheric Composition and Cloud Dynamics

Cloudy Nightside and Clear Dayside

JWST’s sensitivity yet again came through in detecting the varying cloud coverage on WASP-43 b. The nightside appears dimmer and cooler due to thick, high-altitude clouds that trap infrared radiation, while the dayside remains largely clear.

This phase curve, captured by the MIRI low-resolution spectrometer on NASA’s James Webb Space Telescope, tracks the brightness changes of the WASP-43 system as the planet orbits its star. The system shines brightest when the hot dayside of the planet faces the telescope, just before and after it passes behind the star, and grows dimmer as the nightside comes into view. It brightens again after the planet passes in front of the star as the dayside rotates back into view. WASP-43 b, a hot Jupiter located approximately 280 light-years away in the constellation Sextans.

wasp-43 b hot gas giant exoplanet
Credits: Science: Taylor J. Bell (BAERI); Joanna Barstow (Open University); Michael Roman (University of Leicester) Graphic Design: NASA, ESA, CSA, Ralf Crawford (STScI)

Water Vapor and Missing Methane

Both the dayside and nightside atmospheres showed clear signs of water vapor. However, methane, expected to be found on the cooler nightside, was notably absent. The fast-moving winds prevent methane formation, maintaining a uniform atmospheric chemistry across the planet.

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NASA’s James Webb Space Telescope has significantly advanced our understanding of exoplanetary weather with its detailed observations of WASP-43 b

Using mid-infrared light and advanced modeling, researchers have painted a comprehensive picture of the planet’s dynamic atmosphere. These discoveries are vital for future explorations of exoplanetary atmospheres and potentially habitable worlds.

WASP-43 b: A hot Jupiter orbiting 280 light-years away.

Tidal Locking: One side always faces the star, resulting in extreme temperature differences.

High-Speed Winds: Equatorial winds reaching 5,000 mph transport heat across the planet.

Cloud Dynamics: Thick clouds on the nightside and clear skies on the dayside.

Atmospheric Composition: Presence of water vapor; absence of methane due to rapid atmospheric mixing.

FAQ: Understanding WASP-43 b and Beyond

1. What is WASP-43 b?

WASP-43 b is a hot Jupiter exoplanet, similar in size to Jupiter but with much higher temperatures due to its close proximity to its star.

2. Why is WASP-43 b tidally locked?

The planet's orbit is so close to its star that gravitational forces have caused it to have the same rotational period as its orbital period, resulting in one side always facing the star.

3. How did JWST map the weather on WASP-43 b?

JWST used its Mid-Infrared Instrument (MIRI) to measure light variations over a 24-hour period, allowing researchers to create a detailed temperature map of the planet.

4. What temperatures are observed on WASP-43 b?

Temperatures reach nearly 2,300 degrees Fahrenheit (1,250 degrees Celsius) on the dayside and drop to 1,100 degrees Fahrenheit (600 degrees Celsius) on the nightside.

5. What are supersonic winds?

Supersonic winds on WASP-43 b exceed 5,000 miles per hour, transporting heat from the dayside to the nightside.

6. What is the significance of the missing methane?

The absence of methane on the nightside suggests rapid atmospheric mixing, preventing methane formation.

7. What role do clouds play in WASP-43 b’s atmosphere?

Thick clouds on the nightside trap infrared light, making the side appear cooler than it would without clouds.

8. How does WASP-43 b’s atmosphere compare to Earth’s?

While vastly different in composition and temperature, studying WASP-43 b's dynamic atmosphere can help scientists understand weather patterns on other planets.

9. What is phase curve spectroscopy?

A technique measuring tiny changes in brightness as a planet orbits its star, helping to infer atmospheric conditions.

10. Why is this discovery important for future exoplanet studies?

Mapping weather on exoplanets like WASP-43 b helps scientists understand their atmospheres and edges us closer to finding potentially habitable worlds.


  • NASA, WASP-43 b, link, [27.05.2024]
  • NASA, NASA’s Webb Maps Weather on Planet 280 Light-Years Away, link, [27.05.2024]
  • NASANASA’s Hubble Maps the Temperature and Water Vapor on an Extreme Exoplanet, link, [27.05.2024]
  • Bell, T.J., Crouzet, N., Cubillos, P.E. et al. Nightside clouds and disequilibrium chemistry on the hot Jupiter WASP-43b. Nat Astron (2024)., [27.05.2024]