Milestone: Astronomers Discover Water Vapor on a Super-Earth

Milestone: Astronomers Discover Water Vapor on a Super-Earth

Astronomers have discovered for the first time the presence of water in the atmosphere of a planet orbiting within the habitable zone of a distant star. The exoplanet has been named K2-18b and it is located outside of our solar system.

If confirmed by further studies, this will be the only planet known to have both water in its atmosphere and temperatures that could sustain liquid water on a rocky surface.

However, its red dwarf star is quite active which means it could be exposing the planet to lots of radiation, which would make K2-18b a much more hostile place than Earth.

"With so many new super-Earths expected to be found over the next couple of decades, it is likely that this is the first discovery of many potentially habitable planets", said Ingo Waldmann, study co-author and lecturer in extrasolar planets at the University College London's Centre for Space Exochemistry Data. At nearly three times Earth's diameter and between 7 and 10 times its mass, K2-18b is a super-Earth, a type of planet abundant in the galaxy, even though it's absent from the solar system. We assume that any planet capable of supporting life has to exist within the habitable zone (also sometimes called the "Goldilocks zone") of its host star.

Their research was published on arXiv which found compelling evidence of the existence of water vapour on the planet.

Sadly, exoplanets in orbit around red dwarfs are considered poor candidates for habitability, owing to the propensity of this group of stars to produce tremendously powerful and frequent solar flares.

Water vapor had previously only been discovered in the atmospheres of super-hot gas giants, like Jupiter.

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Hubble observations resulted in a distinct water signal, but the UCL researchers weren't certain about the amount of water packed into the atmosphere of K2-18b, or whether liquid water exists at the surface. Their study, which appears in Nature Astronomy, also suggests that K2-18b's atmosphere contains hydrogen and helium. The London data suggest water vapor makes up anywhere between 0.01% and 50% of the atmosphere - "quite a big range", Waldmann acknowledged.

K2-18b is one of hundreds of "super-Earths" - exoplanets with masses between those of Earth and Neptune - found by Kepler. However, it brings us closer to answering the fundamental question: "Is the Earth unique?", Tsiaras said.

However, some scientists who were not a part of the research, said the planet should not be described as "habitable".

In addition to water, Hubble also detected traces of hydrogen, an observation that intrigued Tom Louden, a physicist at the University of Warwick and an expert on exoplanetary atmospheres.

The red dwarf star is an active one, however, which is likely exposing the exoplanet to more radiation than Earth receives. This planet is large and has a thick atmosphere, making it easier, but in principle planets the same size and temperature as Earth could be analyzed this way as well. Given its mass and radius, K2-18 b is not a gaseous planet, but has a high probability of having a rocky surface.

With the next generation of telescopes, such as the James Webb Space Telescope and the ARIEL space mission, we will be able to find more information on the chemical composition, cloud coverage and structure of the atmosphere of K2-18 b.

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