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Scientists at University College London (UCL) describe an exoplanet that is the only one of its kind to have both water and temperatures that can support life. The K2-18b exoplanet, discovered by NASA's Kepler Space Telescope in 2015, is located about 110 light-years from Earth.
"As of today, we know that K2-18b has an atmosphere and water, making it the best-known candidate for livability," said lead author of the study. , Angelos Tsiaris.
Kepler scientists initially determined that K2-18b was about twice the diameter of the Earth. More recently, European astronomers have used a terrestrial telescope to examine the effects of K2-18b on its planetary star in orbit, which has allowed them to measure the mass of the exoplanet about 8 times that of the Earth.
With this diameter and mass, K2-18b is classified as a super-Earth, larger than our planet and smaller than the big gaseous planets like Jupiter.
The sun of the exoplanet is a red dwarf smaller and colder than ours, and it was found that K2-18b resided in the habitable zone. This means that the planet has a proximity to its sun that would allow liquid water to exist.
The UCL team used the Hubble Space Telescope wide-field camera 3 to detect visible, ultraviolet and near-infrared wavelengths. The experts searched for chemical signatures of the K2-18b atmosphere to determine the presence of water.
"The measures involved were extremely difficult," said Tsiaris Time magazine. "It's like trying to identify a person on a crowd of ten thousand people."
The study revealed that the exoplanet contains an abundance of water that accounts for up to 50% of the atmosphere. The team did not share this discovery right away.
"I had the results a year ago," Tsiaris told Time. "At first we did not know exactly what it meant, but we knew we had something exciting. It took us a year of repetitive data analysis to make sure our claims were correct. To bring you to these two facts – there is an atmosphere and there is water – has taken a lot of effort. "
"If planets like Earth are very common, we can say that life is very common."
The study is published in the journal Nature Astronomy.
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By Chrissy Sexton, Earth.com Editor
Image credit: ESA / Hubble, Mr Kornmesser
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