Birmingham-led team finds reflective atmosphere on lava planet

An international team including University of Birmingham astrophysicist Dr Anjali Piette announced on Oct. 29, 2026 that a reflective cloud layer wraps rocky lava planet TOI-561 b, about 280 light years from Earth, and acts like a sunscreen.

The researchers used the James Webb Space Telescope to observe TOI-561 b for 37 hours, tracking nearly four full circuits around its star. JWST collected the infrared data used for the analysis, and the observations spanned almost four full orbits, giving the researchers a complete phase curve of the planet as it moved around its star. Professor Lisa Dang of the University of Waterloo explained that the phase curve technique measured how brightness and heat changed throughout the orbit, showing reflected starlight and heat redistribution that point to an atmosphere.

The data revealed a global atmosphere unsuitable for life that reflects roughly three-quarters of incoming starlight, a reflectivity comparable to Venus. The reflectivity suggests the upper atmosphere or cloud deck sends much of the stellar energy back to space. Initial observations had shown the dayside was far cooler than expected for a bare, dark rock so close to its star, prompting the team to investigate where the missing heat went.

Observing the complete orbit let the team see the night side of TOI-561 b for the first time, and that hemisphere’s temperature was not warm enough to explain the missing heat. Because TOI-561 b is tidally locked, its night side never receives direct starlight, so its measured temperature helps distinguish between heat redistribution and reflectivity. The missing energy could either move to the night side or be reflected away before the planet absorbed it. Atmospheric circulation moves some heat from the day side to the night side, lowering temperatures on the star-facing side.

The team compared the observations with a computer climate simulation, which suggests dayside clouds of silicate minerals including silicon dioxide and magnesium silicate could act like sunscreen. Silicate clouds made of minerals like silicon dioxide and magnesium silicate could form on the dayside and reflect starlight before it heats the surface, acting as a planetary-scale sunshade. Reflective silicate clouds may cool TOI-561 b and stop the heat expected for a rock with no atmosphere.

Dr Anjali Piette said the discovery challenges current theories because a heavily irradiated rocky planet like TOI-561 b should have shed its atmosphere billions of years ago, yet evidence suggests it still has a significant atmosphere today. Piette notes that standard planetary evolution models predict atmospheric loss for a world so close to its star, making the detected atmosphere surprising. The University of Birmingham frames the result as a challenge to assumptions that strongly irradiated rocky planets cannot keep atmospheres over billions of years.

The finding builds on earlier work by Dang, Piette, and colleagues showing that TOI-561 b likely has a thick atmosphere renewed by gases released from its molten interior, providing context for the new reflectivity findings. A Carnegie Institution for Science-led team reported on December 10, 2025, that TOI-561 b, a scorching hot super-Earth about 560 light-years away, has a thick, volatile-rich atmosphere and is likely covered in a magma ocean. EarthSky reports that the Carnegie-led announcement came on December 10, 2025, adding to growing evidence that ultra-short-period rocky planets can keep thick atmospheres despite high temperatures, and this earlier study gives a different distance for TOI-561 b than the October 2026 Birmingham-led study.

TOI-561 b has a radius 1.4 times Earth’s and a mass about twice Earth’s, with significantly lower density than Earth, and a thick atmosphere could account for that discrepancy. The planet’s low density relative to an Earth-like composition motivated the hypothesis that a thick atmosphere inflates its apparent radius. The planet orbits its star in 10.56 hours and is broiling hot; scientists thought it was too small and hot to retain an atmosphere. TOI-561 b completes an orbit in only 10.56 hours, placing it extremely close to its star, and JWST/NIRSpec measurements showed its dayside temperature was about 3,200 degrees Fahrenheit (1,760 degrees Celsius), far cooler than the roughly 4,900 degrees Fahrenheit (2,700 degrees Celsius) expected for a bare rock with no atmosphere.

The Carnegie team proposed a thick atmosphere made of volatiles such as water, oxygen and carbon dioxide, with winds cooling the dayside by moving heat to the night side, and possibly bright silicate clouds reflecting starlight. The volatile-rich atmosphere of water, oxygen and carbon dioxide could transport heat and obscure the surface, explaining the cooler-than-expected dayside. Tim Lichtenberg of the University of Groningen postulated an equilibrium between the magma ocean and atmosphere, where gases feed the atmosphere while the magma ocean reabsorbs them, requiring the planet to contain far more volatiles than Earth. The Carnegie team published its results in The Astrophysical Journal Letters on December 11, 2025.

The composition of TOI-561 b’s atmosphere remains an open question; it could be a dense carbon dioxide blanket like a much hotter Venus, or rich in sulfur dioxide vented from a volcanic moon comparable to Io. Carbon dioxide would resemble a superheated Venus, while sulfur dioxide would point to volcanic outgassing like Jupiter’s moon Io. Piette said the planet may have begun with an unusually large supply of gases, or its ocean of molten rock may act as a planet-wide volcano constantly feeding its atmosphere.

Dang said the team wants to know whether TOI-561 b’s atmosphere is more like Venus or like an extreme Io, and that longer-wavelength JWST observations could reveal how such a hot world kept its atmosphere for billions of years. Dang says longer-wavelength JWST observations could distinguish between a Venus-like carbon dioxide atmosphere and an Io-like sulfur dioxide atmosphere, and test how the atmosphere survived for billions of years. Together, these observations point to the presence of an atmosphere, Dang said.

The study, A Highly Reflective Atmosphere on the Lava World TOI-561b Revealed by JWST/NIRSpec Phase Curves, appeared in The Astronomical Journal in 2026; volume 172, issue 4, page 239, DOI 10.3847/1538-3881/ae9763. The Astronomical Journal paper lists authors from institutions in the UK, Canada, the USA, Australia, and the Netherlands, and the study is open access. The research team included the University of Birmingham, Université de Montréal, University of Waterloo, University of Oxford, Carnegie Institution for Science and its Observatories, MIT, University of Sydney, University of Exeter, University of Groningen, University of Toronto, University of Hawai’i, University of Cambridge, and Stanford University.