Webb telescope spots an “impossible” atmosphere on ancient super-Earth

The interesting part here is not that Webb found another weird exoplanet. It is that, according to a new paper in The Astrophysical Journal Letters, a class of planets many researchers expected to be stripped bare may be holding onto serious atmospheres anyway.

According to Carnegie Science and NASA’s Webb team, the planet TOI-561 b is an ultra-short-period rocky world: roughly 1.4 Earth radii, about twice Earth’s mass, and a year that lasts 10.56 hours. It orbits about one-fortieth of the Mercury-Sun distance, so one hemisphere is in permanent daylight and the surface is likely molten.

The result, according to the peer-reviewed paper led by Johanna Teske and colleagues (ApJL DOI: 10.3847/2041-8213/ae0a4c; preprint at arXiv), is that TOI-561 b’s dayside emission does not look like a bare rock. The team used Webb’s NIRSpec in the 3 to 5 micron range and found a cooler-than-expected dayside signal. According to NASA’s summary of the measurement, a bare-rock interpretation points to around 2,700 C, while the observed dayside is closer to 1,800 C.

That temperature gap matters because it implies heat redistribution and radiative effects that are hard to get from naked rock alone. According to the paper abstract, the planet’s density is also relatively low for an irradiated rocky world, reported as about 4.3 ± 0.4 g/cm³, which keeps the atmosphere hypothesis in play alongside non-Earth-like interior composition models.

The team’s interpretation, according to Carnegie and NASA, is a volatile-rich atmosphere above a magma ocean, with possible wind transport from dayside to nightside and additional cooling from atmospheric absorption and perhaps silicate clouds. Co-author Tim Lichtenberg described this as a “wet lava ball,” according to both outlets.

Here’s the bigger point for builders and investors watching space science and instrumentation: this is exactly the kind of measurement Webb was built for. Not pretty images, but brutal thermodynamic constraint on planetary models. If this result holds up across follow-on analyses, it weakens a very popular simplification—that heavily irradiated small planets should all end up as desiccated bare rock.

It also opens a practical modeling problem. According to the paper and NASA release, TOI-561 b may be losing gas to space while also replenishing volatiles through magma-atmosphere exchange. That means long-term atmospheric survival may be an equilibrium problem, not a yes/no switch. For exoplanet science, that shifts effort toward coupled interior-atmosphere models and better phase-curve constraints, not just radius-mass cataloging.

The caveat is straightforward: this is strong evidence, not final closure. According to NASA, these are first results from Webb General Observers Program 3860, which observed the system for more than 37 hours, and the team is still analyzing the full dataset to map temperatures around the full orbit and narrow composition. In plain terms, we likely know the atmosphere is there, but we do not yet know its exact mix.

Analysis: what looks “impossible” here is probably a reminder that planetary evolution is messier than rule-of-thumb charts. TOI-561 b may be less an exception than a sign our previous priors were too clean for lava-world physics.

ScienceDaily’s write-up is a syndication of institutional reporting, according to the article itself, so the real primary attribution belongs to the Carnegie-led team, NASA’s mission reporting, and the ApJL paper.

What to watch next is whether full-orbit mapping and retrieval work can distinguish between a water-rich volatile envelope, mineral vapor contributions, and cloud-driven cooling. If those pieces tighten, this moves from “surprising detection” to a new baseline for how we think about ultra-hot rocky planets.