LHS 1140 b atmosphere: first air found on a rocky world in the habitable zone

On July 16, 2026, a team led by Collin Cherubim of Harvard University reported something astronomers had chased for years. They had found the first clear sign of a LHS 1140 b atmosphere on a rocky planet inside another star's habitable zone. The paper appeared in Science after observations from September 2024. I have followed exoplanet news for a while, and this one felt different. It was not another candidate or model. It was a measured signal.

The planet sits about 48 light-years away in Cetus. It orbits a cool red dwarf. It is 5.6 times the mass of Earth and about 70 percent larger in radius. The same study showed the LHS 1140 b atmosphere leaking helium into space. That leak proves air is there, and that it has lasted for more than 3 billion years.

Why the LHS 1140 b atmosphere matters for habitability

More than 6,000 exoplanets are now confirmed. Dozens are rocky and sit at the right distance for liquid water. Until July 2026, none of those had a confirmed atmosphere. That gap is what makes the LHS 1140 b atmosphere hard to ignore, as summarized in the ScienceDaily report on the finding.

Most of these worlds orbit red dwarfs, the most common stars. They are small and cool, so temperate orbits sit close in. Young red dwarfs throw off strong X-ray and ultraviolet light that can strip air. LHS 1140 b kept its envelope for billions of years despite that glare. Many textbooks said such planets were likely bare rocks. One counterexample proves bare rock is not the only outcome.

Star forming region with gas and dust, similar to where red dwarf systems take shape. Image via Unsplash.

How the LHS 1140 b atmosphere was detected from 48 light-years away

The team watched starlight pass through the air. When LHS 1140 b crossed its star, a small part of that light filtered through upper layers. That method is called transit spectroscopy. The group used WINERED on the 6.5 meter Magellan Clay Telescope in Chile to look for helium near 10,833 angstroms. Helium gives a clean signal when it escapes, which makes this exoplanet helium detection stand out.

On September 23, 2024, two planets crossed at once. LHS 1140 c moved first. LHS 1140 b followed 39 minutes later. The team took 70 spectra over 6.5 hours. LHS 1140 c showed no helium. LHS 1140 b showed absorption near 1.24 percent, starting before ingress and lingering after, like a tail.

This was the first time this method worked on a rocky exoplanet atmosphere. WINERED runs near 68,000 resolution, which split the triplet from stellar noise. A 2025 visit showed no helium, which points to variation in escape rather than error.

What helium tells us about this super-Earth atmosphere

Helium alone cannot support life. It is inert. So why did a helium line cause so much attention? Because it answers a yes or no question. Does this world have air? The answer is yes, and the LHS 1140 b atmosphere is the proof.

Loss runs near 3 x 10 to the 8 grams per second. That is around 220 tons per second, roughly a blue whale every second. Over 3 billion years that adds up, yet air remains. The starting reservoir was large or deeper layers keep feeding the top.

The mix is odd. Hydrogen is scarce up top, near 1 to 1,000 versus helium. Light hydrogen escapes first while helium stays behind. Theorists predicted such worlds more than a decade ago. Cherubim built a model from mass, radius, age, orbit, and X-ray flux that named this planet first. The later Carnegie report on the detection shows how that prediction matched the spectra.

Water and carbon dioxide are likely lower down if they exist. At 226 K water can condense and rain back down while helium sits on top where escape happens. Past JWST spectra ruled out a clear hydrogen rich envelope yet left room for nitrogen or water. That fits a layered super-Earth atmosphere. Density points the same way. At 1.73 Earth radii and 5.6 Earth masses the planet is less dense than bare rock, matching 9 to 19 percent water. Try our exoplanets template to sort these types by density.

Earth's thin atmosphere seen from orbit. LHS 1140 b holds a more extended helium envelope. Image via Unsplash.

What the LHS 1140 b atmosphere means for the search for life

Does this mean the planet is inhabited? No. The authors are careful on that point. Air is required for surface life as we know it. It is not enough on its own. We still lack bulk composition and proof of liquid water. The CNN coverage of the result states that limit in simple terms.

Still, the result shifts the search for life in three ways.

First, red dwarf planets can keep air. This LHS 1140 b atmosphere survived more than 3 billion years. A world that cannot hold air that long is a poor place to look for life.

Second, water is back on the table. If 9 to 19 percent of the mass is water, a deep ocean is possible. JWST will look for vapor below the helium. For background, see our explainer on biosignatures and the search for life beyond Earth.

Third, ground telescopes can now screen targets. WINERED showed a ground spectrograph can pick out escaping helium. Students can practice this triage in our playground for instant quizzes by pasting mass, radius, and irradiation.

"Collin analyzed the planets we knew about and predicted that this one would have a helium atmosphere. Then he organized telescope time, got the data, and the detection was statistically rock solid."

David Charbonneau, Harvard Astronomy

That quote shows method, not luck. Predict from physics, test with new data, check with a control planet in the same system.

How this rocky exoplanet atmosphere compares to other planets

TRAPPIST-1 has seven Earth size planets, yet JWST has found no air on the inner ones. LHS 1140 b is larger and circles a quieter, older star, so it holds gas better. Our piece on a volcanic exoplanet shaped by tides shows the other end, where heat can remake air fast. For a cold giant contrast, see our note on JWST water ice clouds on a distant super Jupiter.

Mars is the local lesson. It once had thicker air and flowing water. Loss to space thinned it. If you want that baseline, start with our guide to Mars habitability and subsurface water.

Some early JWST papers found no features and leaned airless. Those sample different heights at different wavelengths. A helium top with a heavy lower deck can look flat in one band and sloped in another. The BBC report on the first atmosphere notes JWST will need years to sort water from stellar effects. The control still stands out. LHS 1140 c was observed the same night with the same pipe and showed nothing.

Night sky over Earth. LHS 1140 lies about 48 light-years away in Cetus. Image via Unsplash.

Numbers and context for this habitable zone exoplanet

If you need a fast answer for class or a quiz, use this box. What was found? Helium escaping from a temperate rocky planet, the first confirmed LHS 1140 b atmosphere. When? Spectra from September 23, 2024, paper July 16, 2026. Where? 48 to 49 light-years away, around red dwarf LHS 1140. How? Transit spectra at 10,833 angstroms, 1.24 percent depth. Why does it matter? It proves a habitable zone exoplanet with rock can keep air for billions of years. Background values come from the papers and the Wikipedia summary of LHS 1140 b.

For study, cover the right column and say each value out loud. Note the dates. 2024 yes, 2025 no. Escape varies with the star. A second exoplanet helium detection has not yet repeated here.

Frequently asked questions

Is LHS 1140 b habitable? No proof yet. Air is present, but surface conditions are unknown. The planet gets about 42 percent of Earth's light. Without warming it would be cold. We need water and carbon dioxide readings first.

Why helium and not oxygen? Helium in this state absorbs where ground instruments can split it. Oxygen, water, and carbon dioxide need other bands, mostly from space. The helium line samples the top where gas leaves. A super-Earth atmosphere can hide lower layers this way.

Does the 2025 miss cancel the 2024 hit? No. Same instrument, same pipe, different star weather. A modest drop in high energy light can push the line under the limit. The 2024 depth was 1.24 percent. The 2025 limit was near 0.6 percent. More transits will map the cycle.

How is this different from TRAPPIST-1? Size and calmness. LHS 1140 b is 1.73 Earth radii and 5.6 Earth masses. TRAPPIST-1 planets are near 1 Earth radius. More mass holds gas better. An older star strips less. That is why a habitable zone exoplanet here kept air while smaller ones look bare so far.

Could it be a mini Neptune? That was on the table. Past spectra ruled out a clear low weight hydrogen shell. Density allows a water rich body. Helium on top with heavy gas below fits better. The final call needs eclipse data. For now, rock plus evolved air is the simplest match for the LHS 1140 b atmosphere.

What should JWST look for next? Water, carbon dioxide, and nitrogen lower down. If water appears with a stable signal, the air is likely long lived. If spectra stay flat, the lower deck may be thin or cloudy. Either answer shows how a super-Earth atmosphere behaves over time.

What to watch next

The field now has a template. That order saves scarce space time. It also gives students a clear chain to remember:

• Start from model predictions and pick a short list
• Test for escaping helium from the ground with a neighbour as control
• Send winners to JWST for deeper bands and repeat across cycles

I expect a busy four to five years. JWST will stare for water. Ground teams will re observe helium to catch the next high night. Each new rocky exoplanet atmosphere will test whether the LHS 1140 b atmosphere is rare or common.

To keep this fresh, go to the Mind Hustle playground, paste five facts from the table, and test yourself twice. Try our quiz flow on mindhustle.net and recall mass, radius, period, distance, and helium depth.