Lava world TOI-561 b keeps its atmosphere behind a shield of rock clouds
A lava planet 280 light-years from Earth should have no air at all. Yet the James Webb Space Telescope has found it wrapped in a bright, reflective atmosphere that scientists cannot yet fully explain.
TOI-561 b is a rocky super-Earth, about 1.4 times as wide as our planet, racing around its Sun-like star in under 11 hours, so close its dayside is molten rock. Astronomers expected its star’s fierce radiation to have stripped away any atmosphere long ago.
Instead, Webb found the planet bounces back roughly three-quarters of the starlight that hits it, about as reflective as Venus. Its dayside is also much cooler than a bare rock should be: about 1,800 degrees Celsius, where a dark, airless world would bake at around 2,700 degrees. The team, led by Lisa Dang at the University of Waterloo, watched it for 37 hours with Webb’s NIRSpec instrument, tracking its brightness and heat through nearly four full orbits. That gave them their first look at the nightside, which was too cool to hold the missing heat.
Computer models point to clouds made of silicate minerals, silicon dioxide and magnesium silicate. There, rock vaporises, rises and condenses into bright clouds that act like sunscreen and help the atmosphere survive. The study, published in The Astronomical Journal, builds on earlier hints of an atmosphere found in 2025. What the air is made of is still unknown: it could be carbon dioxide, like a far hotter Venus, or sulphur dioxide, the gas from volcanoes on Jupiter’s moon Io.
Why it matters
It challenges a basic idea in exoplanet science: that small rocky worlds blasted by their stars must end up bare. Most rocky planets Webb has studied so far, mainly around cooler red dwarf stars, look airless. TOI-561 b orbits a more Sun-like star and still holds on to a substantial atmosphere, which suggests the rules may be different around stars like our own. If rock clouds can shield an atmosphere for billions of years, more lava worlds may have air than expected.
What happens next
The team now wants to find out what the atmosphere is made of. The next question, Dang said, is whether it resembles Venus or an extreme version of Io. Longer-wavelength Webb observations could help answer that.
This article is for general information and education only. It is not legal or financial advice.
Sources
- https://phys.org/news/2026-10-oddball-lava-world.html (Phys.org, 31 October 2026)
- https://www.zmescience.com/science/news-science/lava-world-sunscreen/ (ZME Science, 28 October 2026)
