A recently discovered exoplanet is “potentially habitable,” according to a newly published study.
Known as K2-18b, the planet is 124 light-years from Earth and is in the “habitable zone” around its star, a sign that “it’s possible for the planet to host liquid water at habitable conditions beneath its hydrogen-rich atmosphere,” according to a statement from the University of Cambridge.
“The thermodynamic conditions at the surface of the H2O layer range from the supercritical to liquid phases, with a range of solutions allowing for habitable conditions on K2-18b,” the researchers wrote in the study’s abstract. “Our results demonstrate that the potential for habitable conditions is not necessarily restricted to Earth-like rocky exoplanets.”
Artist’s impression of K2-18b. (Credit: Amanda Smith)
“There is a reasonable chance that the planet hosts a large ocean underneath the atmosphere at pressures and temperatures similar to those in the Earth’s oceans,” the study’s lead author, Nikku Madhusudhan, said in an interview with Newsweek.
Given its size – 2.6 times the radius and 8.6 times the mass of Earth – it’s likely that K2-18b, which was discovered in 2015, is a smaller version of Neptune. Ordinarily, that would lead researchers to believe there is a “significant hydrogen ‘envelope’ surrounding a layer of high-pressure water, with an inner core of rock and iron,” but that is not the case with K2-18b. Instead, they found the hydrogen envelope is “not too thick” and there may be a water layer that “could have the right conditions to support life,” the statement added.
“We wanted to know the thickness of the hydrogen envelope — how deep the hydrogen goes,” the study’s co-author, Matthew Nixon, explained. “While this is a question with multiple solutions, we’ve shown that you don’t need much hydrogen to explain all the observations together.”
Researchers are quick to caution, however, that because it’s located in the habitable zone does not necessarily mean life exists.
“Water vapor has been detected in the atmospheres of a number of exoplanets but, even if the planet is in the habitable zone, that doesn’t necessarily mean there are habitable conditions on the surface,” Madhusudhan added in the statement. “To establish the prospects for habitability, it is important to obtain a unified understanding of the interior and atmospheric conditions on the planet — in particular, whether liquid water can exist beneath the atmosphere.”
The study has been published in The Astrophysical Journal Letters.
More than 4,000 exoplanets have been discovered by NASA in total, approximately 50 of which were believed to be potentially habitable as of September 2018. They have the right size and the right orbit of their star to support surface water and, at least theoretically, to support life.