Research

Water vapor found on an 'Earth-sized' exoplanet 110 light-years from home

Water vapor found on an 'Earth-sized' exoplanet 110 light-years from home

Eight times the mass of Earth and twice as big, K2-18b orbits in its star's "habitable zone" at a distance - neither too far nor too close - where water can exist in liquid form, they reported in the journal Nature Astronomy. The exoplanet has been named K2-18b and it is located outside of our solar system.

"This is not only because super-Earths like K2-18b are the most common planets in our galaxy, but also because red dwarfs - stars smaller than our Sun - are the most common stars".

"This is the first time that we have detected water on a planet in the habitable zone around a star where the temperature is potentially compatible with the presence of life", she was quoted as saying in a BBC News report.

Discovered in 2015, K2-18b is one of hundreds of so-called "super-Earths" - planets with less than ten times the mass of ours - spotted by NASA's Kepler spacecraft.

The results revealed the molecular signature of water vapour, and also suggest the presence of hydrogen and helium in the planet's atmosphere. The planet, K2-18b, is certainly not habitable by us, as it's a mini-Neptune that may not have any solid surface and is likely to have a hydrogen/helium-rich atmosphere.

Future space missions are expected to detect hundreds more in the coming decades.

While water already has been identified in the atmospheres of hot gas giants circling other stars, the latest findings represent the first detection of water vapor in the atmosphere of another type of exoplanet, Tsiaras said. It's large relative to its host star, meaning that a larger fraction of the starlight will pass through the atmosphere on its way to Earth when the planet is between the star and us.

Its atmosphere was studied by astronomers at the University College London (UCL).

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Their research was published on arXiv which found compelling evidence of the existence of water vapour on the planet. It orbits a red dwarf star 110 light-years away from Earth in the Leo constellation. And aside from water vapour, its atmosphere contains mostly hydrogen gas - a molecule that makes up less than 1 part per million of our own atmosphere.

With data from the Hubble Space Telescope, water vapor has been detected in the atmosphere of an exoplanet within the habitable zone of its host star. However, it brings us closer to answering the fundamental question: "Is the Earth unique?" study first author Dr Angelos Tsiaras said in a statement issued by UCL.

Further studies are required to estimate cloud coverage and the percentage of atmospheric water present, the researchers said.

There's still a chance it could be bathed in a huge ocean, though, which would be more suitable for life, Abel Mendez, director of the Planetary Habitability Laboratory at the University of Puerto Rico, who was not involved in either study, told Daniel Oberhaus at WIRED.

Not quite Earth 2.0 Even though it has water, K2-18b may be hostile to life since it is likely to be exposed to more high-energy radiation.

Benneke stated that although water exists in liquid water clouds on K2-18 b, the rain falls through thick gas before it hits the surface, heating it so it becomes gas before it reaches the planet's surface.

Researchers must wait for more sophisticated tools, such as the long-delayed James Webb Space Telescope, to reveal more details about the distant world.