Scientists Map True 3D Shape of Distant Exoplanet Using New Telescope Technique
An international team used James Webb Space Telescope data to reveal that WASP-17b, a hot Jupiter 1,000 light-years away, is slightly egg-shaped rather than perfectly spherical.
What happened
Researchers published findings in Nature Astronomy showing the first detailed three-dimensional shape of exoplanet WASP-17b using a new technique called transit mapping. The technique measures starlight passing through different regions of the planet's atmosphere as it transits in front of its host star, providing more precise measurements than traditional methods that average data. WASP-17b was found to be slightly egg-shaped due to an equatorial bulge created by hot atmospheric gases circulating from its scorched dayside to its cooler nightside. The deformation matches theoretical predictions for a tidally locked hot Jupiter and demonstrates that astronomers can now investigate the shapes and atmospheric dynamics of distant exoplanets with unprecedented detail.
Context
This advancement represents a shift from simplified mathematical models (perfectly spheres) to characterizing the actual physical features of exoplanets as three-dimensional objects. The technique validates theoretical understanding of how extreme stellar heating and atmospheric circulation shape gas giants orbiting very close to their stars. The successful application of transit mapping could enable astronomers to study atmospheric circulation and weather patterns on other distant worlds in coming years. WASP-17b's deformation, though subtle, reveals how the extreme conditions on this world—intense heating and atmospheric winds—physically reshape the planet's structure.