What To Know
- LHS 1140 b has captured the attention of scientists because of its position in the habitable area from its star, a low-mass red dwarf about one-fifth the size of the Sun.
- This scenario suggests an icy planet with a potential liquid ocean at the substellar point, an area of the planet’s surface that would always face the system’s host star due to the planet’s synchronous rotation that is similar to Earth’s Moon.
- According to the modelsif LHS 1140 b does indeed have an Earth-like atmosphere, it could look like a snowball with an ocean about 4,000 kilometers in diameterequivalent to half the surface area of the Atlantic Ocean.
An international team of astronomers recently identified LHS 1140 b, a temperate exoplanet located about 48 light-years from Earth in the constellation Cetus. This discovery, made by the Université de Montréal, could mark a significant advance in the search for habitable worlds beyond our solar system. Observations made with the James Webb Space Telescope (JWST) and other space telescopes have indeed provided insight into the nature of this fascinating world, whose characteristics suggest the possible presence of an atmosphere and a liquid water ocean.
A new Super-Earth
LHS 1140 b has captured the attention of scientists because of its position in the habitable area from its star, a low-mass red dwarf about one-fifth the size of the Sun. Exoplanets in this “Goldilocks zone” have temperatures that could support liquid water, a crucial element for life as we know it. This discovery is particularly exciting because LHS 1140 b is one of the closest exoplanets to the solar system, making its study more accessible with current technologies. Naturally, the first questions the researchers asked were about the nature of LHS 1140 b: was it a mini-Neptune, a small gas giant, or a super-Earth, that is, a rocky or water-rich planet larger than Earth? Extensive analyses ruled out the scenario of a mini-Neptune. The evidence suggests instead that LHS 1140 b could be a super-Earth potentially possessing a nitrogen-rich atmosphere similar to that of our planet. This atmosphere is essential for retaining heat and supporting a stable climate, conditions necessary for the presence of liquid water. If confirmed, LHS 1140 b would be an ideal candidate for future habitability studies. Observations of the James Webb Telescopesupplemented by those from Spitzer, Hubble and TESS, were crucial in understanding the characteristics of LHS 1140 b. This is the first time we have observed evidence of an atmosphere on a habitable exoplanet. Detecting atmospheres on small rocky worlds is a major goal of JWST” notes astronomer Ryan MacDonald of the University of Montreal.
A ball of ice containing a huge ocean
More interestingly, estimates based on the accumulated data reveal that LHS 1140 b is less dense than expected for a rocky planet of Earth-like composition, suggesting that 10 to 20% of its mass could be composed of water. This scenario suggests an icy planet with a potential liquid ocean at the substellar point, an area of the planet’s surface that would always face the system’s host star due to the planet’s synchronous rotation that is similar to Earth’s Moon. According to the modelsif LHS 1140 b does indeed have an Earth-like atmosphere, it could look like a snowball with an ocean about 4,000 kilometers in diameterequivalent to half the surface area of the Atlantic Ocean.
The exoplanet could be a completely ice-covered world (left) or an ice world with a substellar liquid ocean and a cloudy atmosphere (center). LHS 1140 b is 1.7 times the size of our planet Earth (right) and is the most promising habitable-zone exoplanet to date in our search for liquid water beyond the solar system. Credits: B. Gougeon/Université de Montréal The researchers now plan to continue observations with JWST to confirm the nitrogen gas signature and look for other gases that could indicate conditions favorable to life. Compared to other habitable-zone exoplanets, such as those in the TRAPPIST-1 system, LHS 1140 b has the advantage of having a less turbulent environment, making it easier to observe its atmosphere.
