This artist’s concept shows what a thick atmosphere above a vast magma ocean on exoplanet TOI-561 b could look like. Measurements of light captured from the planet’s dayside by NASA's James Webb Space Telescope suggest that in spite of the intense radiation it receives from its star, TOI-561 b is not a bare rock.
TOI-561 b is the innermost of four planets orbiting TOI-561, a 10-billion-year-old G-type star located roughly 280 light-years from Earth, in the constellation Sextans. Classified as an ultra-short period (USP) planet, TOI-561 b orbits just 0.01 AU from its star (1% the distance between Earth and the Sun, or about one million miles), completing one circuit in less than 11 hours.
Although the star is somewhat smaller and cooler than the Sun, the planet orbits so close that its dayside surface temperature must far exceed the melting temperature of typical rock. (Planets that orbit this close to their stars are thought to be tidally locked, with a permanent dayside that faces the star at all times, and a permanent nightside in eternal darkness.) A thick atmosphere rich in volatiles like water, oxygen, and carbon dioxide would distribute heat around the planet, causing the nightside as well as the dayside to be molten.
This illustration is based on spectroscopic data and other indirect observations. Webb has not captured any images of TOI-561 b.
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