Hubble Finds First Water Vapor on Habitable-Zone Exoplanet

Water vapor has been spotted on a “habitable zone” planet 110 light years away

Rocky super-Earth named most habitable known world beyond solar system

Astronomers announced this week they have detected water vapor in the atmosphere of a planet outside of the solar system, making it the first exoplanet in a star's "habitable" zone to show signs of moisture.

Over the past three years, scientists have obtained thousand of observations of eight transits where the K2-18b passed between the host star and Earth.

In an unprecedented discovery, researchers have found water outside Earth, on an exoplanet- a planet out of our solar system.

Results have revealed the molecular signature of water in the exoplanet's habitable zone and temperatures that could sustain liquid water on a rocky surface.

"Finding water in a potentially habitable world other than Earth is incredibly exciting", said lead-author Angelos Tsiaras, also from UCL.

Given the high level of activity of its red dwarf star, K2-18b may be more hostile to life as we know it than Earth, as it is likely to be exposed to more high-energy radiation.

In the arXiv.org paper, a team led by University of Montreal astronomer Björn Benneke used the Hubble Space Telescope to pinpoint evidence of a watery atmosphere, noting how it absorbed certain wavelengths of light. Their findings were published this week in the journal Nature Astronomy.

Even if they did, most Earth-like planets are too far from their stars to have liquid water or so close that any H2O has evaporated. Cooler smaller planets are much harder to detect.

While light from the sun takes several minutes to reach Earth, light from K2-18b's star takes a century to reach our planet, "so for us to travel there is impossible", he said.

It's called "K2-18b", dubbed a heavy, larger "super-Earth", and it may have one ingredient necessary to support life as we know it: water. However, it brings us closer to answering the fundamental question: "Is the Earth unique?" said Tsiaras. The exoplanet is probably having a water-based atmosphere but the exact confirmation of helium or hydrogen is still awaited.

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. The London data suggest water vapor makes up anywhere between 0.01% and 50% of the atmosphere - "quite a big range", Waldmann acknowledged. Nitrogen and methane may also be present but with current technology remain undetectable, the study said. Further studies will also aim to estimate cloud coverage and the percentage of atmospheric water present.

Using data from the Hubble Space Telescope's Wide Field Camera 3, astronomers at the Center for Space Exochemistry Data at UCL in the United Kingdom made the discovery.

"In the next five or ten years the James Webb Space Telescope and others are being launched that are created to ... find more details of the atmosphere".

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