'Eyeball' planet spied by James Webb telescope might be habitable

The James Webb Space Telescope (JWST) has found 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 — making it a candidate for a potentially habitable world.

The exoplanet, called LHS-1140b, was first discovered in 2017. Initially, it was thought to be a "mini-Neptune" swirling with a dense mixture of water, methane and ammonia. But the new findings, accepted for publication in The Astrophysical Journal Letters and available on the preprint server arXiv, suggest that the planet is icier and wetter than scientists thought. That means it could support life.

"Of all currently known temperate exoplanets, LHS-1140b could well be our best bet to one day indirectly confirm liquid water on the surface of an alien world beyond our Solar System," first author Charles Cadieux, an astrophysicist at the University of Montreal, said in a statement. "This would be a major milestone in the search for potentially habitable exoplanets."

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Located 50 light-years from Earth, LHS-1140b is roughly 1.73 times wider than our planet and 5.6 times its mass. It is tidally locked to its host star. This means it rotates at the same rate as it orbits its star, keeping its 2,500-mile (4,000 kilometers) melted eye fixed on the cosmic fire. Bound on a close orbit with its star, one 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 of this distance would boil its oceans and make it completely uninhabitable. But because it is a cooler red dwarf, this short distance places 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 enables the telescope to assess the planet's contents as light from its star passes through the planet's hypothetical atmosphere to reach Earth.