Astronomers have announced a historic achievement—the first direct detection of an atmosphere around a rocky planet located within its star's habitable zone. This breakthrough marks a significant step forward in the search for worlds potentially capable of supporting life.
Characteristics of Planet LHS 1140 b
The planet, named LHS 1140 b, is located approximately 48 light-years from Earth. According to the results of the new study, its atmosphere contains helium. In addition to being the first rocky planet with a directly detected atmosphere, it is also the first of its kind found in the so-called habitable zone—the region around a star where temperatures could allow for liquid water on the surface.
Researchers assert that among known exoplanets, LHS 1140 b possesses the greatest number of habitability indicators. The study's lead author, Collin Cherubim, told Space.com that the direct detection of helium in the atmosphere is unprecedented for rocky exoplanets, and its location in the habitable zone adds immense interest for astrobiology and the search for life.
History of Discovery and Planetary Composition
LHS 1140 b is an exoplanet, meaning a planet outside our solar system. It was initially discovered by astronomer Jason Dittman's team in 2017, and he is also involved in the current research. According to Dittman, years of observation were required for scientists to confirm the presence of an atmosphere.
He noted that although the planet was found about ten years ago, the conclusion regarding the atmosphere was only reached now. Dittman emphasized that the planet has a solid surface and is composed of rock. Although the exact nature of this surface is not yet known, the team considers the presence of water on the planet highly probable.
Conditions for Liquid Water
LHS 1140 b orbits a red dwarf—a star smaller and cooler than the Sun. Despite the planet being significantly closer to its star than Earth is to the Sun, this distance is sufficient to maintain temperatures compatible with the 'Goldilocks zone,' which is considered suitable for the existence of liquid water. Researchers believe that the recently discovered atmosphere may help preserve these conditions.
Cherubim hypothesized that the planet likely contains a lot of water. He added that if the atmosphere provides a greenhouse effect, then the conditions we consider habitable on Earth are likely to exist there and could support liquid water.
Similarity to Earth and Scientific Context
Although LHS 1140 b is not an exact copy of Earth, researchers point out two similarities: its composition is a rocky planet, likely with an iron core, and it is now known to have an atmosphere; and its temperature is suitable for liquid water on the surface, which is one of the key requirements for life as we know it on Earth.
Among over six thousand identified exoplanets, the direct confirmation of an atmosphere on a rocky planet in the habitable zone is a unique moment. One of the main challenges is that LHS 1140 b orbits a red dwarf—the most common type of star in the Milky Way, which is about one-third the size of the Sun. These stars remain active for a long time, emitting powerful bursts of radiation, such as solar flares and coronal mass ejections. Typically, such radiation completely destroys the atmospheres of nearby planets, which raised doubts about the ability of rocky planets around red dwarfs to retain an atmosphere over long periods.
Cherubim noted that this discovery demonstrates that at least this rocky planet has managed to retain its atmosphere for billions of years, which is a 'well-founded and reliable way to say yes: atmospheres can survive on rocky exoplanets.' Scientists also suggest that other gases besides helium might be present in the atmosphere, some of which may have been lost in the past due to intense stellar radiation. However, since the star is about six billion years old—several billion years older than the phase of this intense activity—the team believes the planet will continue to retain its atmosphere. Dittman mentioned that while some helium slowly escapes into space, a similar process occurs with Earth's own atmosphere.
Method of Atmosphere Detection
The confirmation of the atmosphere resulted from a theoretical prediction developed by Collin Cherubim during his doctoral dissertation. He explained that it all started with a mathematical model created to study the evolution of rocky planets, from which he made a very specific prediction about this planet.
The researcher decided to apply a method usually used to study gas giants to a rocky planet, which was an unprecedented step. The results fully aligned with his model prediction, allowing the scientific method cycle to be completed.
To test the hypothesis, the team used the Warm Infrared Echelle Spectrograph (WINERED), installed at the Magellan Observatory in Chile. During the same observations, they tracked the transit of LHS 1140 b and another planet in front of its star. Spectroscopic analysis allowed them to identify chemical signatures in the atmospheres of both worlds. While one did not yield results, LHS 1140 b demonstrated a direct and undeniable signal of helium's presence.
Significance of the Discovery
Despite the importance of the finding, researchers emphasize that it does not mean the planet is habitable. Cherubim clarified that he is not claiming there is life on the planet. In the team's view, future observations will allow for the detection of other gases in the atmosphere and the verification of water. Although new research may not confirm habitability or discover life forms, it will significantly expand knowledge about rocky planets of this type. Since LHS 1140 b is the first planet with these characteristics whose atmosphere has been confirmed, it represents an important step toward understanding the evolution of potentially habitable planets and may help answer one of humanity's oldest questions: are we alone in the Universe?
