Astronomers have detected signs of an atmosphere on LHS 1140 b, a rocky exoplanet orbiting within its star’s habitable zone. Published in the journal Science, the study reveals that the planet, located 5.6 times the mass of Earth, likely features a layered atmosphere containing helium and potentially water, according to research from the Carnegie Institution for Science.
Understanding the LHS 1140 b Atmosphere
LHS 1140 b orbits an aging red dwarf star every 24.7 days. First discovered in 2017, the planet has a radius 1.7 times that of Earth. By utilizing a spectrograph on the Magellan telescopes at the Las Campanas Observatory in Chile, researchers observed the planet in 2024. The data provided a rare glimpse of helium gas escaping the planet’s atmosphere, a process driven by extreme ultraviolet radiation and X-rays from its host star.
Shreyas Vissapragada of the Carnegie Institution for Science stated that the team determined the helium was being expelled due to stellar heating. The findings suggest a complex, stratified structure: an upper layer rich in helium and depleted of hydrogen, with lower layers near the surface potentially harboring heavier elements like water.
Did you know? Atmospheric variability is rare. In 2025, follow-up observations failed to detect the same helium signals, suggesting that atmospheric loss on LHS 1140 b may be dynamic and fluctuate on a human-observable timescale.
Why Atmospheric Detection Matters for Habitability
Atmospheres are essential for a planet’s potential to support life. According to the Carnegie Institution for Science, a planetary atmosphere acts as a critical shield against cosmic radiation. It also regulates climate cycles and enables the existence of liquid water on the surface, a fundamental requirement for biological processes.
The ability to analyze these features relies on spectroscopy. When starlight passes through a planet’s atmosphere, it interacts with chemical elements, allowing astronomers to identify the composition of the air. This study marks a significant step forward, as data on rocky planets orbiting within the “habitable zone” of stars outside our solar system remains extremely limited.
Future Trends in Exoplanetary Research
The discovery of a variable atmosphere on LHS 1140 b highlights the need for long-term monitoring of exoplanets.
Frequently Asked Questions
What is the habitable zone?
The habitable zone is the range of orbits around a star where a planet’s surface temperature could allow for the existence of liquid water.
How do scientists know what an atmosphere is made of?
Scientists use spectroscopy. By analyzing the light from the host star as it filters through the planet’s atmosphere, they can identify the unique “fingerprints” of chemical elements present in the gas.
Why did the helium signal disappear in 2025?
Researchers believe that atmospheric loss on LHS 1140 b is variable. The planet’s interaction with the host star’s radiation may change, causing fluctuations in gas escape rates that occur over short timeframes.
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