The Hubble Space Telescope has observed the smallest known extrasolar planet that contains water in its atmosphere, the US (NASA) and European (ESA) space agencies announced Thursday.
“Water on such a small planet is a remarkable discovery,” said Laura Kreidberg of the Max Planck Institute for Astronomy in Germany, co-director of the research. “This brings us closer than ever to describing truly Earth-like worlds.”
The planet in question, GJ 9827d, which is about twice the diameter of Earth, is located in the constellation Pisces, 97 light-years away, or more than 900,000 billion km, according to a NASA and ESA press release.
These officials believe the planet is either a “mini-Neptune” — with a hydrogen-rich, water-charged atmosphere — or a hotter version of Jupiter’s moon Europa, which contains twice as much water as Earth beneath its crust. .
“GJ 9827d could be half water and half rock,” explained Björn Benneke of the University of Montreal, who led the research. “There would be a lot of water vapor on the smaller rock piles.
“Until now, we have not been able to directly detect the atmosphere of such a small planet. And we are gradually getting there,” he added.
For three years, Hubble was able to analyze the wavelength of colors in the atmosphere of GJ 9827d as light from the star it orbits filtered through its atmosphere, and detect the presence of water molecules.
Although this planet has a water-rich atmosphere, its temperature of 425°C makes it uninhabitable.
But the discovery paves the way for further studies of GJ 9827d and similar planets, particularly through the James Webb Space Telescope, which can use its high-resolution infrared images to search for other atmospheric molecules such as carbon dioxide and carbon dioxide. .