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JWST Detects Thick Atmosphere on Ultra Hot Rocky Exoplanet TOI 561 b

JWST Detects Thick Atmosphere on Ultra-Hot Rocky Exoplanet TOI-561 b

The finding challenges long-held assumptions that rocky planets in such harsh environments cannot retain atmospheres.

Written by Gadgets 360 Staff | Updated: 14 December 2025 09:30 IST

JWST Detects Thick Atmosphere on Ultra-Hot Rocky Exoplanet TOI-561 b

Photo Credit: NASA, ESA, CSA, Ralf Crawford (STScI))

James Webb finds a thick atmosphere on ultra-hot rocky exoplanet TOI-561 b

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Highlights

JWST detects gases above a molten super-Earth surface
TOI-561 b orbits its star in just 11 hours
Discovery challenges models of rocky planet evolution

Using‍‌‍‍‌‍‌‍‍‌ the James Webb Space Telescope, astronomers have come across a very hard-to-believe thing. There is an ultrahot exoplanet named TOI-561 b that is 280 light-years away, and even though it is orbiting its star at an ultraclose distance, it has a thick atmosphere. Such a discovery puts in question the basic ideas of planetary evolution and the conditions under which a planet can keep its atmosphere in the most brutal of ‍‌‍‍‌‍‌‍‍‌environments.

Extreme Conditions Defy Expectations

According to the findings, TOI-561 b is a broiling super-Earth with a radius that is one point four times that of Earth, and an orbit that takes only 11 hours. It revolves at a distance of one-fortieth of the distance between Mercury and the sun, thus being tidally bound with one permanent day and night side. Scientists anticipated that this proximity would deplete any atmosphere due to the high stellar radiation in billions of years. But there is something observed here.

Uranus and Neptune May Be Rocky Worlds Not Ice Giants, New Research Shows

A Volatile Mystery

With‍‌‍‍‌‍‌‍‍‌ Webb's Near-Infrared Spectrograph, scientists determined the temperature of the planet's dayside to be around 3,200 degrees Fahrenheit, which is significantly less than the forecasted temperature of 4,900 degrees for a bare-rock kind of planet. The difference in temperatures points to a dense, a few-volatile-rich atmospheric layer which includes water vapour and silicate clouds that reflect the starlight and thus help in temperature moderation.

The researchers hypothesise that the planet is in a state of balance, that is, atmospheric atmosphere are escaping and at the same time being supplied by its magma ocean beneath. This finding changes the way planetary evolution is understood from the very ‍‌‍‍‌‍‌‍‍‌core.

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