JWST Reveals Metal-Poor Atmosphere of TOI-5205b

Astronomers using NASA's James Webb Space Telescope have uncovered unexpected details about the atmosphere of TOI-5205b, a Jupiter-sized exoplanet orbiting a small red dwarf star 283 light-years away in the constellation Vriscka, revealing a composition poorer in heavy elements than its host star or any known gas giant in our solar system.

The planet, which has a radius 1.03 times that of Jupiter and a mass 1.08 times greater, completes an orbit in just 1.63 days around its M4-type star, TOI-5205, which is about 40 percent the mass and size of the Sun. Discovered in 2022 by NASA's Transiting Exoplanet Survey Satellite and confirmed the following year with ground-based observations, TOI-5205b blocks roughly 6 percent of its star's light during transits, providing a strong signal for atmospheric analysis. Researchers observed three such transits with the telescope's Near Infrared Spectrometer, capturing data across infrared wavelengths to probe the planet's gaseous envelope.

The observations, detailed in a study published in The Astronomical Journal, show that the atmosphere contains far fewer heavy elements relative to hydrogen than expected. Its metallicity is lower than that of...