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NASA’s James Webb Space Telescope has helped astronomers find a strange, distant rocky planet that shows traces of a water vapor-rich atmosphere despite its proximity to its star.
Researchers, including those at NASA’s Goddard Space Center, say the exoplanet known as GJ 486 b is too close to its star to be within the habitable zone, with a surface temperature of around 800 degrees Fahrenheit.
The planet, located about 26 light-years away in the constellation Virgo, is about 30 percent larger than Earth and nearly three times as massive, meaning it’s a rocky world with stronger gravity than Earth.
GJ 486 b orbits a red dwarf star, completing one revolution in just under 1.5 Earth days, and is likely tidally locked, with a permanent day side and a permanent night side.
However, signs of water vapor associated with the planet could indicate that it has an atmosphere despite its scorching temperature and proximity to its star, noted the study, published in The Astrophysical Journal Letters.
Previous studies have shown that red dwarf stars are cool enough for nearby planets in close orbits to stay warm enough to potentially harbor liquid water to create a habitable zone for life.
While water vapor has already been seen on gaseous exoplanets orbiting such stars, no atmospheres have been positively detected around a rocky exoplanet.
The researchers, however, warn after the new discovery that the water vapor could be on the star itself, and not from the planet.
“Water vapor in an atmosphere on a hot rocky planet would be a major breakthrough for exoplanet science. But we have to be careful and make sure the star isn’t the culprit,” said study author Kevin Stevenson of Johns Hopkins University in the US.
“We see a signal, and it’s almost certainly due to water. But we still can’t tell if that water is part of the planet’s atmosphere, i.e. the planet has an atmosphere, or if we’re just seeing a water signature coming from the star,” explained study lead author Sarah Moran of the University of Arizona in Tucson.
Scientists spotted the star transiting its star, passing in front of the red dwarf from Earth’s point of view.
If the planet has an atmosphere, then when it transits, starlight would filter through those gases, leaving fingerprints in the light that would allow astronomers to decode its composition.
By decoding the chemical composition of the planet during its transits, astronomers concluded that the most likely source of the signal from the planet was water vapour.
While the water vapor could potentially indicate the presence of an atmosphere, the researchers say the signals could likely come from the star.
There have also been similar reports of water vapor in our Sun sometimes existing in sunspots.
Because GJ 486 b’s host star is much cooler than the Sun, scientists suspect that even more water vapor may be concentrating within its star spots.
This may have created a signal that mimics a planetary atmosphere, they say.
Because the atmosphere of water vapor could gradually erode as the star heats up, even if an atmosphere were present, the researchers say it would have to be constantly replenished by volcanoes from within the planet.
They say more observations are needed to narrow down the amount of water present if there is conclusive evidence of one.
The researchers hope to study data from multiple Webb instruments to conclusively determine the presence of water vapor.
“It’s joining multiple instruments together that will really determine whether or not this planet has an atmosphere,” said Dr. Stevenson.
