"K2-18a Impression" by ESA/Hubble / CC BY 4.0

Water Vapor Detected in Atmosphere of an Alien World Nearly Twice the Size of Earth

Sep 12, 2019

By Chelsea Gohd

Scientists have detected water vapor in the atmosphere of K2-18 b, a potentially habitable alien world about twice the size of Earth. The finding, announced today (Sept. 11), follows a separate study released yesterday announcing the discovery of water vapor, and likely clouds and rain, on the planet.

The far-off planet (it’s about 110 light-years away) was discovered in 2015 by NASA’s Kepler space telescope. The alien world is about two times the size of Earth and eight times as massive. K2-18 b orbits a red dwarf star in the “habitable zone” — the range of distances where liquid water could be stable on a world’s surface.

Scientists with the study published today in the journal Nature Astronomy used data from Hubble Space Telescope observations made from 2016 and 2017 collected by the research team behind yesterday’s study to determine that the exoplanet has water vapor in its atmosphere. K2-18 b is so far the smallest exoplanet that atmospheric water vapor has been discovered on.

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