Agence France-Presse 12. September 2019 09:40:38 IST
Water was discovered for the first time in the atmosphere of an exoplanet with Earth-like temperatures that could support life as we know it, scientists revealed Wednesday.
Eightfold of Earth's mass and twice the size, K2-18b, orbits the "habitable zone" of its star at a distance ̵
"This planet is the best candidate we have outside our solar system" in search of vital signs, co-author Giovanna Tinetti, astronomer at University College London, tells AFP . "We can not assume there are oceans on the surface, but it's a real possibility."
Of the more than 4,000 so far discovered exoplanets, this is the first known to combine a rocky surface and an atmosphere with water. Most exoplanets with atmospheres are huge gas balls, and the handful of rocky planets for which data is available seem to have no atmosphere at all. Even if it does, most Earth-like planets are too far from their stars to have liquid water, or so close that H2O has evaporated.
K2-18b was discovered in 2015 and is one of hundreds of so-called "super" Earth – planets less than ten times our mass – spotted by NASA's Kepler spacecraft.
Future space missions will be in the coming decades Expected to show hundreds more.
Is Earth Unique?
"Water in a potentially habitable other world than Earth is incredibly exciting," said lead author Angelos Tsiaras, also from UCL. "K2-18b is not & # 39; Earth 2.0 & # 39 ;, "he said," but this brings us closer to answering the basic question: is the Earth unique? "
Tsiaras and his team used open source algorithms to bring the starlight analyzing the spectroscopic data collected by the Hubble Space Telescope in 2016 and 2017 filtered through the atmosphere of K2-18b.
They found the signature signature of water vapor iss remains, but computer modeling suggested concentrations between 0.1 and 50 percent. For comparison, the proportion of water vapor in the earth's atmosphere varies between 0.2 percent over the poles and up to four percent in the tropics.
Hydrogen and helium were also detected. Nitrogen and methane may also be present, but with current technology undetectable, the study said. Further research will be able to determine the extent of cloud cover and the percentage of water in the atmosphere.
First of many
water is crucial for finding life, also because it contains oxygen. "As we know, life is based on water," Tinetti said.
K2-18b orbits a red dwarf star – a million billion kilometers – about 110 light years away – in the Leo constellation of the Milky Way, probably more destructive than Earth's.
"It is likely that this is the first of many discoveries of potentially habitable planets," said UCL astronomer Ingo Waldmann, also co-author. "This is not only because super-Earths such as K2-18b are the most common planets in our galaxy, but also because red dwarfs – stars smaller than our Sun – are the most common stars."
The New Generation of Space Star observation tools, led by the James Webb Space Telescope and the European Space Agency (ESA) ARIEL mission, can describe exoplanet atmospheres in much greater detail.
ARIEL, which is scheduled to launch in 2028, will size about 1,000 planets, a large size, enough samples to look for patterns and identify outliers.
"Over 4,000 exoplanets have been discovered, but we do not know much about their composition and nature," Tinetti said. "By observing a large number of planets, we hope to reveal secrets about their chemistry, education, and development."
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