First Water Detected on Potentially ‘Habitable’ Planet

Water vapour has been detected in the atmosphere of a super-Earth with habitable temperatures by UCL researchers in a world first. (Image: University College London)

K2-18b, which is eight times the mass of Earth, is now the only planet orbiting a star outside the Solar System, or “exoplanet,” known to have both water and temperatures that could support life.

The discovery, published in Nature Astronomy, is the first successful atmospheric detection of an exoplanet orbiting in its star’s “habitable zone” at a distance where water can exist in liquid form. First author, Dr. Angelos Tsiaras (UCL Centre for Space Exochemistry Data (CSED)), said:

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The team used archive data from 2016 and 2017 captured by the ESA/NASA Hubble Space Telescope and developed open-source algorithms to analyze the starlight filtered through K2-18b’s atmosphere. The results revealed the molecular signature of water vapor, also indicating the presence of hydrogen and helium in the planet’s atmosphere.

The authors believe that other molecules, including nitrogen and methane, may be present, but with current observations, they remain undetectable. Further studies are required to estimate cloud coverage and the percentage of atmospheric water present.

The planet orbits the cool dwarf star K2-18, which is about 110 light years from Earth in the Leo constellation. Given the high level of activity of its red dwarf star, K2-18b may be more hostile than Earth and is likely to be exposed to more radiation.

K2-18b was discovered in 2015 and is one of hundreds of super-Earths — planets with a mass between Earth and Neptune — found by NASA’s Kepler spacecraft. NASA’s TESS mission is expected to detect hundreds more super-Earths in the coming years.

Co-author Dr. Ingo Waldmann (UCL CSED) said:

The next generation of space telescopes, including the NASA/ESA/CSA James Webb Space Telescope and ESA’s ARIEL mission, will be able to characterize atmospheres in more detail, as they will carry more advanced instruments.

ARIEL is expected to launch in 2028 and will observe 1,000 planets in detail to get a truly representative picture of what they are like. Professor Giovanna Tinetti (UCL CSED), co-author and Principal Investigator for ARIEL, said:

Dr. Tsiaras added:

Secretary of State Andrea Leadsom said:

Chris Lee, the UK Space Agency’s Chief Scientist, said:

Dr. Colin Vincent, Head of STFC’s Astronomy Division, said:

Provided by: University of Chicago Medicine [Note: Materials may be edited for content and length.]

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