Water vapor has been detected in the atmosphere of an exoplanet with habitable temperatures.
K2-18b is the only planet orbiting a star outside our Solar System known to have water and temperatures that could support life.
The discovery, made by a team of University College London (UCL) researchers, was published this week in the journal Nature Astronomy.
This marks the first successful atmospheric detection for an exoplanet orbiting in its star’s “habitable zone,” at a distance where H2O can exist in liquid form.
“Finding water in a potentially habitable world other than Earth is incredibly exciting,” according to study author Angelos Tsiaras, a research associate at the UCL Center for Space Exochemistry Data (CSED).
“K2-18b is not ‘Earth 2.0’ as it is significantly heavier and has a different atmospheric composition,” Tsiaras said in a statement. “However, it brings us closer to answering the fundamental question: Is the Earth unique?”
Using archive data captured by the Hubble Space Telescope in 2016 and ’17, the team developed open-source algorithms to analyze starlight filtered through K2-18b’s atmosphere.
Their results revealed the molecular signature of water vapor, as well as the presence of hydrogen and helium in the planet’s atmosphere.
And while nitrogen and methane may also be present, they remain undetectable—for now. Further studies are needed to estimate cloud coverage and the percentage of atmospheric water present.
Identified in 2015 by NASA’s Kepler spacecraft, K2-18b orbits the red dwarf K2-18 some 110 light years from Earth in the Leo constellation.
It is one of hundreds of super-Earths—planets with a mass between Earth and Neptune—spotted by Kepler; NASA’s new TESS mission is expected to uncover hundreds more.
“Our discovery makes K2-18b one of the most interesting targets for future study,” co-author Giovanna Tinetti, UCL physics professor and principal investigator for ESA’s ARIEL mission, said.
More than 4,000 exoplanets have been detected, but scientists still don’t know much about their composition. So the more information we can gather on these celestial bodies, the better.
“This study contributes to our understanding of habitable worlds beyond our Solar System,” Tsiaras added, “and marks a new era in exoplanet research, crucial to ultimately place the Earth, our only home, into the greater picture of the Cosmos.”
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