This Lava World Should Be Bare Rock. Instead, It Wears a ‘Sunscreen’ of Rock Clouds

Webb observations suggest TOI-561 b reflects most of the starlight reaching it. Clouds formed from vaporized minerals could explain its surprising brightness.

TOI-561 b should be a naked ball of lava. The planet orbits so close to its star that a year lasts less than 11 hours, its surface is likely a global ocean of magma, and it has been blasted with radiation for billions of years. That is more than enough time to strip away any air it was born with.

Instead, the James Webb Space Telescope (JWST) found it wrapped in an atmosphere so reflective that it bounces roughly three-quarters of the incoming starlight back into space. According to a new study published in The Astronomical Journal, clouds of silicate minerals hovering above the magma may be the reason, acting like a planet-sized sunscreen.

TOI-561 b sits approximately 280 light-years from Earth. It’s a super-Earth roughly 1.4 times wider than our planet, and hugs its Sun-like star at a distance of less than a million miles, about one-fortieth of the gap between Mercury and the Sun. At that range, it whips around in under 11 hours and is almost certainly tidally locked, with a permanent dayside and a permanent nightside.

This isn’t the first time the planet has raised eyebrows. In late 2025, many of the same astronomers reported in The Astrophysical Journal Letters that the planet was less dense than expected for its size and that its dayside was far cooler than it should be.

A bare, dark rock in that orbit should bake at roughly 4,900°F (2,700°C). JWST measured something closer to 3,200°F (1,800°C). Still hot enough to melt rock, mind you, but that’s a lot of missing heat.

Energy can go to basically only two places. Either winds carry it around to the nightside, or something reflects it back to space before it ever reaches the surface.

To find out which, the team, led by Lisa Dang at the University of Waterloo in Canada, trained JWST’s NIRSpec instrument on the planet for 37 hours straight as it completed nearly four orbits. This kind of observation is called a phase curve. By tracking how the system’s brightness and heat change as the planet swings around its star, astronomers can piece together a rough temperature map of the whole world, nightside included. According to Dang, the phase curve showed that the planet reflects a lot of light and that heat spreads around the globe rather than staying on the sunlit side, both of which signal an atmosphere.

“We measured how the planet’s brightness and heat changed throughout its orbit,” Dang said. “This…revealed that the planet reflects a significant amount of light from its star, and that heat is being redistributed around the planet instead of only on the sunlit side. Together, these point to the presence of an atmosphere.”

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The nightside turned out to be too cool to account for all the missing energy. Some heat is clearly being shuffled around the planet, which alone points to an atmosphere. But most of the answer lies elsewhere. TOI-561 b reflects around 75% of the starlight that hits it. That puts it in the same league as Venus, the most reflective planet in our Solar System. For comparison, Earth reflects only about 30%.

“(T)he evidence suggests it still has a significant atmosphere today,” said Anjali Piette, assistant professor in astronomy at the University of Birmingham. “This raises major questions such as whether the planet started with an unusually large supply of gases or if the ocean of molten rock covering its surface, acts as a planet-wide volcano that is constantly feeding its atmosphere.”

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Simulations from the JWST data point to clouds rich in silicate minerals, namely silicon dioxide (the same compound that makes up quartz and most beach sand) and magnesium silicate. On Earth, these materials make up rocks. On TOI-561 b, it’s hot enough for them to vaporize, rise and condense into bright clouds high above the dayside.

Those clouds would bounce much of the incoming radiation back into space, shading the magma below.

What the rest of the atmosphere is made of is still an open question. One option is a thick blanket of carbon dioxide, much like Venus but turned up several notches. Another is an atmosphere dominated by sulfur dioxide, the gas that Jupiter’s moon Io belches out through its hundreds of active volcanoes. Either way, it’s no place for life as we know it.