JWST maps asymmetrical atmosphere of exoplanet WASP-17b
Astronomers have used the James Webb Space Telescope to indirectly observe the physical shape of an exoplanet for the first time, mapping the structure of the gas giant WASP-17b located roughly 1,300 light-years from Earth. The breakthrough relied on an innovative analysis method called transit mapping.
Mapping the Atmosphere of WASP-17b
WASP-17b is an inflated gas giant with a radius about 1.9 times that of Jupiter, though its mass is only half that of Jupiter and its equilibrium temperature sits near 1,760 Kelvin. Using transmission spectra gathered by the James Webb Space Telescope, researchers discovered that the exoplanet features an asymmetrical atmosphere that is more dilated on its evening side than on its morning side.
Planetary scientists attribute this asymmetry to powerful equatorial jet streams that transport heat from the planet’s permanent day side toward its dark night side. The resulting higher temperatures on the evening side cause local atmospheric expansion, matching predictions from three-dimensional atmospheric circulation models.
An International Research Effort
The findings stem from a collaborative research project between Cornell University in the United States and the University of Bristol in the United Kingdom, applying a transit mapping technique developed in Bristol by astrophysicists David Grant and Hannah Wakeford. Lili Alderson, a Klarman postdoctoral researcher at Cornell University who began the work at Bristol, served as lead author of the study published in Nature Astronomy.
This is a demonstration of feasibility that shows planets are bel and bien three-dimensional objects and that, when they turn around their star, the phenomena we predict actually happen,
Lili Alderson stated in a university release. But passing from numerical simulations to their real observation constitutes a whole other step.
Planets are capricious, their atmospheres complex and chaotic,
Hannah Wakeford, associate professor of astrophysics at the University of Bristol and co-author of the study, added in the release. The fact that all these data concur and reveal to us a representation as structured and dynamic of this giant world situated at more than 1,000 light-years is truly exciting.