Water vapor, and maybe even rain, has been found in the atmosphere of a super-Earth within the habitable zone – in a world’s first. The research was detailed by University College London and University of Montreal researchers in Nature Astronomy and arXiv.
For the first time, water vapor has been detected in the atmosphere of another planet with temperatures that could support life, a new study says.
The planet, known as K2-18b, is eight times the mass of Earth, and is now the only planet orbiting a star outside the solar system, or “exoplanet,” known to have both water and habitable temperatures.
The discovery, published Wednesday in the peer-reviewed British journal Nature Astronomy, is the first successful detection of an exoplanet orbiting in its star’s “habitable zone,” at a distance where water can exist in liquid form.
“Finding water in a potentially habitable world other than Earth is incredibly exciting, said study lead author Angelos Tsiaras of University College, London. “It brings us closer to answering the fundamental question: Is the Earth unique?”
K2-18b was discovered in 2015 and is one of hundreds of super-Earths – planets with a mass between Earth and Neptune. With a temperature that’s similar to that of the Earth, “this planet is the best candidate for habitability that we know of right now,” he said.
The detection of water vapor – which is water in its gaseous phase – was made possible with data from the Hubble Space Telescope, Tsiaras said.
The planet orbits the cool dwarf star K2-18, which is about 110 light-years from Earth in the constellation Leo. Given the high level of activity of its red dwarf star, the planet may be more hostile than Earth and is likely to be exposed to more radiation, according to the study.
“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 study co-author Ingo Waldmann, also of University College, London. “This is not only because super-Earths like 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 authors conclude the planet provides an excellent target for follow-up observations, which will provide further insights into the composition and climate of other habitable-zone planets.
“This study contributes to our understanding of habitable worlds beyond our solar system and marks a new era in exoplanet research, crucial to ultimately place the Earth, our only home, into the greater picture of the cosmos,” Tsiaras said.
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