Water discovered for first time in atmosphere of habitable exoplanet

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The team of scientists also discovered that K2-18b has a mass eight times greater's than on planet Earth, which implies that the surface gravity of the planet would be eight times higher than the one on our planet.

This artist's impression shows the planet K2-18b, its host star and an accompanying planet in this system.

As Space.com noted, "Because this study has found evidence for liquid water and hydrogen in this exoplanet's atmosphere and it lies within the habitable zone, there is a possibility that this world is habitable". The exoplanet could be a potential super-Earth (a planet with mass lesser than the masses of ten Earths), hinting at the probability of life outside the solar system.

Future telescopes on Earth and in space should help uncover more Super Earths orbiting red dwarf stars - believed to be the most common planets and stars in our Milky Way galaxy.

A group of astronomers may have found Earth's long-lost cousin, discovering the first ever "habitable" terrestrial planet with water in its atmosphere, according to new research aided by the Hubble telescope.

Working with spectroscopic data captured in 2016 and 2017 by the Hubble Space Telescope, Tsiaras and his team used open-source algorithms to analyse the starlight filtered through K2-18b's atmosphere.

He added: "K2-18b is not "Earth 2.0" as it is significantly heavier and has a different atmospheric composition". Some super-Earths have turned out to be more like sub-Neptunes, with big gaseous envelopes, but this planet's average density is similar to the density of the Moon or Mars.

Now we have for the first time managed to detect water vapour in the atmosphere of an exoplanet that is potentially habitable.

However, we can not say, with current data, exactly how likely the planet is to support life.

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

"However, it brings us closer to answering the fundamental question: Is the Earth unique?". All five planets appear to have a high-altitude haze that weakens water's signal from deeper within their atmospheres. Other molecules, including nitrogen and methane, may be present but they remain undetectable with current observations. The London data suggest water vapor makes up anywhere between 0.01% and 50% of the atmosphere - "quite a big range", Waldmann acknowledged.

The astronomers who comb through data on planetary surveys looking for potentially habitable planets are searching for worlds with certain specific characteristics. Models of planet formation indicate that K2-18b is probably large enough to have hung on to the hydrogen and helium that it started with, but the presence of other gasses in its atmosphere have yet to be determined. K2-18b orbits the dwarf star K2-18 in the Leo constellation, given the high level of activity of its star, K2-18b may be more hostile than Earth and is likely to be exposed to more radiation, NASA said.

They hope that newer technology, such as the James Webb Space Telescope due to launch in March 2021, will be able to unlock more secrets beyond our solar system.

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.

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