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Steam found on a potentially habitable planet: "Possibly this is a water world"


An artist's impression shows K2-18b and its host star. The planet has life-friendly temperatures, and it can have water too.

ESA / Hubble, M. Kornmesser

For the first time, astronomers who look beyond our solar system have discovered water vapor in the atmosphere of a planet where the temperature can also be just right for life.

Exoplanet K2-18b is a super-Earth twice the size of our planet, with eight times the mass. It's also wet, or at least the sky around it is. Researchers found evidence of water vapor when they collected data captured by NASA's Hubble Space Telescope in 2016 and 2017 and ran it through an open source algorithm they developed to analyze distant planets. They published their results Wednesday in the journal Nature.

Water vapor has been found in the atmospheres of other planets, but this is the first time such moisture has been detected on a planet in the star zone of its star, where temperatures could be acceptable, if not pleasant.

More information is needed to determine what type of cloud cover the planet has, how much water is in the atmosphere, and whether things actually form large masses of water on the planet's surface like here on Earth.

"It is quite possible that this is a water world," said co-author Giovanna Tinetti, professor of astrophysics at University College London. But she warned that it was too early to confirm the presence of a kind of sea on the surface.

It is estimated that the temperature of the planet can be between about minus 100 degrees Fahrenheit (minus 73 Celsius) and 150 Fahrenheit (66 Celsius). Of course, it is a great choice, but it is not that far away from the conditions we see here on earth.

"But this planet is not a second earth," said Angelos Tsiaras, a research assistant at UCL. . "It revolves around what we call a red dwarf star … in this environment, space weather is more hostile than here on earth."

Red dwarf stars also called M dwarf stars, are smaller, cooler and brighter than our sun. They are also known for often releasing powerful sunburns that can threaten to irradiate orbiting planets . Fortunately, K2-18, which is 110 light-years from Earth, is not as likely to eject as other M-dwarf stars.

"This one in particular is not very active at all," Ingo Waldmann, lecturer in extrasolar planets at UCL and magazine co-author, told me. "We haven't seen anything deterrent."

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The analysis of the starlight passing through the planet's atmosphere also revealed hydrogen and helium. Future studies can determine if other molecules that are closely linked to life, as we know it, such as nitrogen and methane, also exist.

The researchers are hopeful that the upcoming James Webb Telescope which will be significantly more powerful than Hubble, can provide an even clearer picture of what is happening on distant exoplanets. If conditions are right, you can even add K2-18b to an interstellar itinerary in the distant future.

"Our discovery makes K2-18b one of the most interesting targets for future studies," Tinetti said.

Originally published September 11 at 10 am PT.

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