The James Webb Space Telescope (JWST) has discovered that a distant world discovered several years ago could be an “eyeball” planet with an iris-like ocean surrounded by a sea of solid ice. This could make the planet a candidate for a potentially habitable world.
The exoplanet, dubbed LHS-1140b, was first discovered in 2017. It was initially thought to be a “mini-Neptune” orbiting a dense mix of water, methane and ammonia. But the new findings, accepted for publication in The Astrophysical Journal Letters and available on the preprint server arXivsuggest that the planet is icier and wetter than scientists thought. That means life is possible.
“Of all the currently known temperate exoplanets, LHS-1140b may be our best chance to one day indirectly confirm liquid water on a planet’s surface. alien world outside our solar system,” first author Charles Cadieuxan astrophysicist at the University of Montreal, said in a statement“This would be an important milestone in the search for potentially habitable exoplanets.”
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LHS-1140b is located 50 light-years from Earth and is about 1.73 times wider than our planet and 5.6 times more massive. It is tidally locked to its star. This means that it rotates as fast as it orbits its star, keeping its 4,000-kilometer-long molten eye trained on the cosmic fire. Bound into a close orbit to its star, a year for the planet is just under 25 Earth days.
If LHS-1140b’s star were a main-sequence star like the Sun, an orbit this far would boil its oceans and make it completely uninhabitable. But because it’s a cooler red dwarf, this close distance puts the planet right in the middle of the “Goldilocks zone” — the perfect distance from its star for liquid water to exist on the planet.
To study the exoplanet, the researchers used JWST’s Near-Infrared Imager and Slitless Spectrograph, which allow the telescope to assess the planet’s contents as light from the star travels through the planet’s hypothetical atmosphere to reach Earth.
By looking at the wavelengths of the absorbed light, the astronomers found signs of nitrogen, a key ingredient in Earth’s atmosphere. Separate calculations also revealed that the planet is not dense enough to be made of rock.
Taken together, these results seem to rule out a rocky world or a mini-Neptune world in favor of a world located in an icy sea.
While most of the planet could be frozen, the researchers noted that the “iris” side could reach temperatures of 20 degrees Celsius at the surface — warm enough to create a viable pool for marine life on the frozen world.
“Detecting an Earth-like atmosphere on a temperate planet pushes Webb’s capabilities to the limit – it’s achievable; we just need a lot of observing time,” said co-author René Doyona physicist at the University of Montreal, said in the statement. “The current indication of a nitrogen-rich atmosphere needs confirmation with more data. We need at least another year of observations to confirm that LHS 1140b has an atmosphere, and probably another two or three years to detect carbon dioxide.”