Light-Years Away ‘Super Earth’ Could Have Conditions to Support Life
Oct 29 2019
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.
First author, Dr Angelos Tsiaras (UCL Centre for Space Exochemistry Data, CSED), said: "Finding water on a potentially habitable world other than Earth is incredibly exciting".
However, the discovery brings astronomers closer to answering the fundamental question of how unique Earth is in the universe, the scientists said. Now, as observed by NASA's Hubble Space Telescope, a habitable-zone exoplanet, dubbed as K2-18b, presents water vapor in its atmosphere.
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Apart from detecting water in the atmosphere, scientists also revealed that K2-18b is located within the habitable zone of the star, which makes it a potential contender to host alien life. In the constellation of the water snake (Hydra) discovered exoplanets orbiting the 31 light-years distant star GJ 357. So, if simply finding them is so challenging, determining the molecules in their atmospheres is even more hard.
"Probably, this is the first of several discoveries of potentially habitable planets", explained UCL astronomer Ingo Waldmann, plus a co-author.
Think your friends would be interested? K2-18b is likely to consist of silicates, like the earth, Mars and Venus, as well as ice cream.
Nitrogen and methane may also be current but with present technology stay undetectable, the analysis stated.
Although the precise composition of the atmosphere can not be extracted - Hubble is brilliant, but its not technically capable of determining chemical signatures like other dedicated telescopes - the authors modelled different scenarios to find the best fit possible with their data.
The planet, however, has a gravity eight times as strong as Earth's, which means that an average man on its surface would weigh about half a ton.
K2-18 b's gravitational pull is better understood, because we know the planet's mass and diameter.
"The fact we can now make observations that allow us to work out what's in the atmosphere of a planet twice the Earth's radius, orbiting a star that is just over a quadrillion kilometres away, is just awesome".
An interesting characteristic of super-Earths is that a lot of them are likely to be water worlds-terrestrial planets covered entirely by a deep global ocean.
"Our discovery makes K2-18b one of the most interesting targets for future study", co-author Giovanna Tinetti, UCL physics professor and principal investigator for ESA's ARIEL mission, said.
So far, attempts to gauge the atmospheres of terrestrial super-Earths have failed, either because of thick clouds (as was the case for Gliese 1214 b and HD 97658 b), a lightweight, featureless atmosphere of just hydrogen and helium (as for 55 Cancri e), or no atmosphere and no clouds at all (as for six of the planets in the TRAPPIST-1 system). This gas accretion would have more than doubled the planet's radius and increased its volume eightfold.
The next generation of space telescopes, including the James Webb Space Telescope, will be able to characterize exoplanet atmospheres in more detail.
Exoplanets that are Jupiter-sized or larger are easier to find than smaller ones, particularly those closer to the size of Earth.
Björn Benneke (University of Montreal) led a team in applying for time on the Hubble Space Telescope, observing the planet as it crossed the face of its star.
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