A team of astronomers has used the James Webb Space Telescope to settle a years-long debate about one of the nearest rocky worlds beyond our solar system. LHS 3844 b, a super-Earth roughly 49 light-years from us, has no detectable atmosphere whatsoever. Its sun-facing hemisphere is a scorched wasteland where temperatures climb past 770 degrees Celsius, hot enough to liquefy aluminum and zinc.
The result, reported in Nature Astronomy in May 2026, draws on mid-infrared observations from Webb’s MIRI instrument spanning 5 to 12 microns. The thermal emission spectrum the team captured is strikingly featureless: no absorption signatures from carbon dioxide, sulfur dioxide, or any other gas that would betray even a thin atmosphere. What the data show instead is a dark, bare rock baking under relentless stellar radiation.
What the data actually show
LHS 3844 b is slightly larger than Earth and orbits an M-dwarf star so closely that a single “year” lasts just 11 hours. That proximity locks the planet tidally, fixing one hemisphere in permanent daylight and the other in permanent night. The new Webb observations, collected with the MIRI Low Resolution Spectrometer, confirm that no atmospheric layer is redistributing heat between the two sides. The dayside absorbs stellar energy and radiates it straight back into space, while the nightside stays frigid.
This is not the first time LHS 3844 b has been flagged as airless. In 2019, a team led by astronomer Laura Kreidberg published Spitzer Space Telescope phase-curve data in Nature showing a stark day-night temperature contrast and negligible heat redistribution. That result strongly suggested no thick atmosphere was present. But Spitzer worked in a single infrared band and could not chemically fingerprint the surface or rule out specific gases. Webb’s spectroscopic approach goes a decisive step further: it directly examines the shape of the planet’s thermal glow across a broad wavelength range, matching predictions for what a dark, bare rocky surface should look like under MIRI observation. Simulated spectra published by NASA before the observations were taken anticipated almost exactly the featureless profile that Webb recorded.
The finding fits a pattern that has been building across multiple Webb programs. Separate observations of TRAPPIST-1 b and TRAPPIST-1 c, two rocky planets orbiting another nearby M-dwarf, also found no evidence of thick atmospheres. Taken together, these results suggest that small, tidally locked rocky planets hugging red dwarf stars face punishing conditions for atmospheric retention.
What scientists still do not know
Confirming the absence of a detectable atmosphere is not the same as knowing everything about the surface beneath it. The exact mineral composition of LHS 3844 b remains an open question. Pre-observation modeling explored how Webb might distinguish basalt from other silicate surfaces based on subtle spectral differences in the mid-infrared. The new data are consistent with a dark surface, but whether that darkness comes from basaltic rock, iron-rich minerals, or some other composition has not been resolved with high confidence. Observations at additional wavelengths or with improved signal-to-noise ratios could help narrow the possibilities.
Quantitative upper limits on surface pressure are also imprecise. The combined Spitzer and Webb datasets constrain any atmosphere to something too thin to produce measurable heat redistribution or spectral features, but they do not pin down an exact pressure ceiling the way a direct transit spectroscopy measurement might. An extremely tenuous gas layer, comparable to Mercury’s wispy exosphere, could still exist without contradicting anything in the current data. Researchers have been careful to describe the planet as having “no detectable atmosphere” rather than claiming a perfect vacuum.
Then there is the question of how LHS 3844 b ended up this way. M-dwarf stars are notorious for intense ultraviolet and X-ray flaring, particularly during their first few hundred million years. That bombardment can strip volatile-rich envelopes from close-in planets over geological time. But whether LHS 3844 b lost a primordial atmosphere to stellar activity, never accumulated one during formation, or shed its gases through some other mechanism is not something the spectroscopic data alone can answer. Resolving that puzzle will require comparing atmospheric retention across a larger sample of rocky planets at similar orbital distances around M-dwarfs, a survey that Webb is only beginning to make possible.
How to weigh the two lines of evidence
Two distinct observational techniques underpin the “no atmosphere” conclusion, and understanding the difference matters for evaluating how strong the case really is.
Spitzer’s phase curves tracked how the planet’s brightness changed as it orbited, revealing how heat moves (or fails to move) across the surface. That single-band photometry could measure the day-night temperature contrast but could not identify specific gases or diagnose surface composition. Webb’s secondary eclipse spectroscopy works differently. By measuring the combined light of star and planet, then subtracting the star’s contribution when the planet passes behind it, astronomers isolate the planet’s own thermal emission across a broad infrared range. The resulting spectrum can reveal or rule out molecular absorption features and constrain what the surface is made of.
The combination of a steep day-night temperature contrast from Spitzer and a featureless emission spectrum from Webb is what makes the case so robust. Neither dataset alone would be as convincing. Phase curves without spectroscopy leave room for exotic atmospheric compositions; spectroscopy without phase curves cannot confirm the absence of heat redistribution.
There are limits to acknowledge. If LHS 3844 b somehow hosted a patchy atmosphere confined to localized depressions or craters, the planet-wide signal might still appear airless. And an atmosphere dominated by molecules that happen to be spectrally quiet between 5 and 12 microns could, in principle, evade detection. Scientists consider both scenarios unlikely given current atmospheric models, but they are part of the reason conclusions are framed conservatively.
What this means for the search for habitable worlds
The verdict on LHS 3844 b reaches well beyond a single scorched planet. M-dwarfs are the most common stars in the Milky Way, and a large share of the rocky exoplanets discovered to date orbit these cool, dim suns at close range. If close-in M-dwarf planets routinely lose their atmospheres, that reshapes expectations for where habitable, Earth-like conditions are most likely to exist. Instead of hugging their stars in the traditional “habitable zone” defined for M-dwarfs, potentially life-friendly planets may need to orbit farther out, where stellar flares are less destructive and surface temperatures are moderate enough for liquid water.
The result also gives astronomers a critical baseline. By confirming what an airless rocky planet looks like in the mid-infrared, the LHS 3844 b dataset becomes a reference template. When Webb or future observatories examine other small worlds, any deviation from this pattern, such as a muted day-night contrast or a prominent molecular absorption band, will stand out more clearly as evidence of an atmosphere, cloud cover, or unusual surface chemistry.
Perhaps most practically, the study demonstrates the power of combining telescopes across generations. Spitzer’s phase curves first raised the flag; Webb’s spectroscopy delivered the confirmation. Similar multi-step campaigns will likely be necessary to characterize many other rocky exoplanets, especially those too small or faint for any single instrument to decode on its own. LHS 3844 b, once just another catalog entry, now serves as the clearest portrait yet of what bare rock looks like under an alien sun.
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*This article was researched with the help of AI, with human editors creating the final content.
