James Webb Space Telescope Maps Lopsided Atmosphere on WASP-17b
Astronomers using the James Webb Space Telescope have discovered that the scorching exoplanet WASP-17b possesses an asymmetrical atmosphere that extends farther outward on its evening side. Located approximately 1,300 light-years from Earth, the giant gas world has a mass roughly 0.8 times that of Jupiter but measures twice as wide, giving it a puffy consistency comparable to a marshmallow.
“This is proof of concept that planets are in fact 3D objects, and that consistently, as they go around their star, what we predict should be happening is happening,” said lead author Dr. Lili Alderson, a Klarman Postdoctoral Fellow at Cornell University who began the research while at the University of Bristol. The findings were published in Nature Astronomy on Wednesday (Oct. 14), following observations gathered in March 2023 through the JWST TST DREAMS programme.
Transmission Strings Technique Reveals Atmospheric Protrusions
To investigate the exoplanet’s atmospheric structure, researchers utilized an innovative technique called transmission strings. The method examines starlight passing through the outer edges of the planet’s atmosphere as it crosses in front of its parent star. Traditional models combine light measurements from the entire atmospheric boundary into a single average spectrum, but the new approach separates information from different regions.
“Rather than assuming your atmosphere is a circle with the same radius all the way around, our technique allows you to pull out different distances from the center to the edge of the planet,” Dr. Alderson explained, describing the advance as moving from a simple ring to identifying specific locations of interest. Co-author Dr. Hannah Wakeford, Associate Professor in Astrophysics at the University of Bristol, noted that the resulting structured picture of the distant world was exciting given the complexity of planetary atmospheres.
Extreme Winds Drive Asymmetrical Bulge on Tidally Locked World
WASP-17b orbits its host star in under four Earth days and is tidally locked, meaning one hemisphere permanently faces the star while the other remains in perpetual darkness. The newly mapped atmospheric distortion occurs precisely near the planet’s equator on the evening side. Powerful atmospheric winds transport heat away from the permanently illuminated dayside toward the cooler nightside, causing the gas on the evening side to expand outward and create a lopsided profile.
The modelling successfully identified specific protruding features in this region that researchers figuratively characterized as gemstones. The observed temperature and chemical variations closely match theoretical predictions and computer models, establishing a useful reference point for studying the more than 6,000 exoplanets confirmed so far.
Frequently Asked Questions About WASP-17b
What is the distance between Earth and WASP-17b?
WASP-17b is located approximately 1,300 light-years away from Earth.
How long does it take WASP-17b to complete one orbit?
The exoplanet completes a full orbit around its parent star in under four Earth days due to its extremely close proximity.
When were the JWST observations of WASP-17b conducted?
The observations were gathered in March 2023 as part of the JWST TST DREAMS programme, with findings published in Nature Astronomy in October.