According to Phys.org, researchers using NASA’s James Webb Space Telescope have detected the strongest evidence yet for an atmosphere on a rocky exoplanet, the ultra-hot super-Earth TOI-561 b. The planet, with a radius 1.4 times Earth’s, orbits its star in less than 11 hours from a distance of less than one million miles, making it tidally locked. Observations with Webb’s NIRSpec instrument showed its dayside temperature is about 3,200°F (1,800°C), far cooler than the 4,900°F expected for a bare rock, pointing to an atmosphere redistributing heat. The team, led by Johanna Teske of Carnegie Science, published in The Astrophysical Journal Letters, suggesting the planet has a thick, volatile-rich atmosphere above a global magma ocean. This helps explain its anomalously low density and challenges the idea that small, close-in planets can’t retain atmospheres. The data comes from Webb’s General Observers Program 3860, which observed the system for over 37 hours.
Why this is a big deal
Here’s the thing: we’ve been finding these ultra-short period planets for years, and the prevailing wisdom was basically that they’d be stripped bare. Think about it. You’re a rocky world, sitting a stone’s throw from your star, getting blasted with radiation for billions of years. How do you hold onto an atmosphere? You shouldn’t. That’s the textbook answer. But TOI-561 b is clearly not following the textbook. It’s not just a naked, scorched rock. It seems to be wrapped in a thick blanket of gas, which is actively cooling its hellish dayside. That alone forces a major rethink of planetary evolution in extreme environments.
The “wet lava ball” theory
So what’s going on? The researchers, including co-author Tim Lichtenberg, have a fascinating theory. They think there’s an equilibrium. The planet must be incredibly volatile-rich—packed with gases like water vapor—more so than Earth. Gases are constantly outgassing from the global magma ocean to feed the atmosphere, but the molten interior is also sucking them back in. Lichtenberg calls it a “wet lava ball.” That’s a brilliant, evocative phrase. It’s not a dry, dead world. It’s a dynamic, churning, gassy mess. The presence of possible silicate clouds, which could reflect starlight, adds another layer of complexity. This isn’t a simple system; it’s a complex geochemical factory operating at insane temperatures.
Implications for other worlds
This discovery has huge ripple effects. TOI-561 b orbits a star that’s twice as old as our sun and iron-poor, from the Milky Way’s thick disk. That means it formed in a very different, more ancient chemical environment. Its composition could be a window into what planets were like when the universe was younger. And if *this* planet can hold an atmosphere, what about others we’ve written off? It breathes new life into the search for atmospheres on other rocky exoplanets, even the ones in seemingly hostile orbits. The technique Webb used here—measuring the secondary eclipse—is the same one being deployed on the TRAPPIST-1 planets. Suddenly, the prospects for finding atmospheres there seem a bit brighter.
What comes next
Now, the team is diving into the full dataset from that marathon 37-hour observation. The goal is to map the temperature all the way around the planet, from the super-heated dayside to the (presumably) cooler nightside. That will give us a stunning thermal map of this world. They also want to narrow down the actual composition of the atmosphere. What gases are making up this thick shroud? Is it water vapor, carbon dioxide, something else? Answering that will tell us about the planet’s interior and its formation history. This is just the first result from this specific Webb program. It’s a powerful proof-of-concept that Webb can do this delicate detective work on small, rocky worlds. I think we’re about to see a flood of similar studies, each one chipping away at our old assumptions and painting a wilder, more diverse picture of what planets can be. The universe, it seems, is a lot more inventive than we gave it credit for.
