Astronomers using the James Webb Space Telescope have mapped the changing shape of an exoplanet atmosphere for the first time, revealing that the hot Jupiter WASP-17b is physically more inflated on its star-facing side than on its nightside, according to findings published in Nature Astronomy and reported by Mirage News.
Mapping WASP-17b With Transmission Strings
Researchers developed a novel method called transmission strings to overcome the traditional limitation of exoplanet observation, which typically averages atmospheric features into a single spectrum. Led by Dr. Lili Alderson at Cornell University, the research team studied WASP-17b, a giant gas planet orbiting a star 1,300 light-years from Earth. Because the planet sits very close to its host star, it experiences extreme temperatures that inflate its atmosphere. The transmission strings technique tracks the planet as it transits across the face of its star, capturing light from the atmospheric edge, or limb, at different angles during ingress and egress.
Supersonic Winds Drive Atmospheric Asymmetry
As a Hot Jupiter, WASP-17b is tidally locked, meaning one hemisphere permanently faces the star while the other faces the darkness of space. This permanent temperature imbalance generates winds reaching thousands of miles per hour. These supersonic currents transport heat across the evening side, through the nightside where temperatures drop, and back over the morning side toward the dayside. Dr. David Grant of the University of Bristol and co-developer of the method explained that this intense thermal circulation causes the hot side of the planet to physically expand further outward than the cooler side, with a smooth temperature transition over the poles.
Broader Implications for Exoplanet Weather Mapping
The successful application of transmission strings on WASP-17b confirms that atmospheric chemical compositions and temperature shifts closely match theoretical models. These findings build upon previous observations of the same planet that identified clouds made of quartz in its atmosphere. According to the research team, including Professor Nikole Lewis at Cornell University and University of Bristol Associate Professor Hannah Wakeford, this empirical method provides a vital stepping stone toward differentiating conditions across various exoplanet latitudes and eventually mapping weather-scale climate patterns on distant worlds.
Frequently Asked Questions About Exoplanet Atmospheres
How does the transmission strings method work?
The technique captures spatial information by measuring starlight filtering through the exoplanet’s atmosphere specifically during ingress and egress, the periods when the planet is only partially crossing the stellar disk. Researchers then fit these measurements with a series of different atmospheric shapes to determine the best mathematical match compared to a perfectly circular profile.
What makes WASP-17b different from typical planets?
WASP-17b is classified as a hot Jupiter, a giant gas world orbiting extremely close to its host star 1,300 light-years from Earth. It experiences intense stellar heat that drives supersonic winds of thousands of miles per hour and creates an asymmetric, highly inflated atmosphere.