JWST finds a "shiny" lava planet that reflects light like Venus

A planet so close to its star that its surface should be a sea of molten rock is turning out to be surprisingly bright. New observations from the James Webb Space Telescope (JWST) show that the lava world TOI-561 b reflects roughly three-quarters of the starlight that reaches it, about as much as Venus does, according to a study published on 27 October 2026.

For astronomers, that is an odd result. A bare, dark rock this hot should soak up almost all the light that hits it. A planet that bounces most of it back is more likely to be wearing something: clouds.

A world with a 10-hour year

TOI-561 b is a "super-Earth", a rocky planet about 1.4 times the radius of Earth and roughly twice its mass, according to NASA's exoplanet catalog. It was found in 2020 when it passed in front of its star, and it circles that star in only about 0.4 days, less than 11 hours. It sits less than a million miles from its star, which NASA says is about one-fortieth of the distance between Mercury and the Sun. At that range it is tidally locked, so one side is always in daylight.

The planet also has an unusually low density for its size, which makes it a puzzle even before the new result. You can find its basic numbers in the NASA Exoplanet Archive overview.

First clue: the day side was too cool

In December 2025, a team using JWST's NIRSpec instrument reported that the planet's day side was far cooler than expected. A bare rock at that distance should reach about 2,700 °C, but Webb measured closer to 1,800 °C. NASA described it as the strongest evidence yet for an atmosphere on a rocky planet outside our solar system, suggesting a thick, gas-rich layer above a global magma ocean that moves heat around the planet.

Second clue: it is shiny

The new study looks at the planet in a different way. Webb watched TOI-561 b for 37 hours, covering nearly four of its orbits, and measured how the combined light of the star and planet changed as the planet circled. This technique, called a phase curve, shows how hot each side is and how much light it reflects.

The result: the planet reflects about 75% of the starlight it receives. The night side is not warm enough to explain the missing heat on its own, so the atmosphere appears to carry some heat from day to night.

Computer models suggest the reflective layer could be silicate clouds, made of compounds such as silicon dioxide (SiO2) and magnesium silicate (MgSiO3). On the day side, they would act like a giant sunscreen, sending light back to space before it reaches the surface.

What the air is made of is still unknown

The team has not pinned down the gases. It could be a thick blanket of carbon dioxide, like a much hotter Venus, or an atmosphere rich in sulphur dioxide, like Jupiter's volcanic moon Io.

Planets this close to their stars are expected to lose their air over billions of years. Dr Anjali Piette of the University of Birmingham, a co-author of the new paper, said: "Our discovery challenges current theories." The project was led by Professor Lisa Dang of the University of Waterloo in Canada, and the paper appears in The Astronomical Journal. You can read the University of Birmingham summary or the ScienceDaily report.

Why this matters

Studying atmospheres on small rocky planets is one of the hardest jobs in exoplanet science, and TOI-561 b is one of the few such worlds where JWST can already tell us something. Each new observation helps narrow down how rocky planets keep, or lose, their air, which is key when astronomers later look for cooler, more Earth-like worlds. More of Webb's exoplanet results are collected on NASA's Other Worlds page.

Follow Webb yourself

JWST does not orbit Earth. It stays near the Sun–Earth L2 point, about 1.5 million kilometres away, and you can watch its position on our live JWST tracker. To see why it parks there, read why JWST orbits L2, or compare it with its predecessor in Hubble vs James Webb. To see where Webb sits among the planets, open our Solar System Live map.