Water vapor was found in the atmosphere of the exoplanet GJ 9827d, located just 97 light-years from Earth. This is the smallest world so far where this chemical compound has been observed. The discovery shows that even in our galactic neighborhood there may be planets with water-rich atmospheres.
Astronomers using belonging to NASA The Hubble Space Telescope discovered water vapor in the atmosphere of the planet GJ 9827d. This seemingly unremarkable world was first observed in 2017. It orbits close to the red dwarf star GJ 9827 in the constellation Pisces, just 97 light-years from Earth. It is also relatively small
The riddle of the atmosphere
As Bjorn Benneke from the University of Montreal, a member of the team studying GJ 9827d, explained, this is the first time scientists have managed to look directly into the planet’s atmosphere and find evidence that celestial bodies with water-rich atmospheres may orbit other stars. The dimensions of the planet also turned out to be important – it is the smallest, closest to Earth extrasolar world known to us, which has water in the atmosphere.
– Water on such a small planet is a breakthrough discovery – added Laura Kreidberg from the Max Planck Institute for Astronomy, co-author of the analysis. “This brings us closer than ever to characterizing Earth-like worlds.”
Water vapor was detected thanks to spectroscopic studies. However, researchers are not sure what type of atmosphere they are dealing with – whether it is composed mainly of hydrogen with a small amount of water vapor, or whether it consists mainly of water left over from the original hydrogen-helium atmosphere, which evaporated under the influence of radiation.
Scientists noted that despite the water content in the atmosphere, GJ 9827d is not a friendly place for organic life. The temperature there reaches 427 degrees Celsius, which means that the planet resembles Venus more than Earth.
The team is currently considering two scenarios. In one of them, GJ 9827d is a miniature version of Neptune, with a residual decaying atmosphere rich in hydrogen and water. If this is true, the planet must have formed farther from its host star, in cooler conditions, and then for some reason began to migrate towards it. The hydrogen was heated and escaped, or continues to escape, from the planet’s weak gravity.
Alternatively, it could be a warmer version of Europa, a moon of Jupiter that has twice as much water under its crust as Earth. Such a celestial body could have formed closer to the star. “The planet GJ 9827d could be half water and half rock. There would be a lot of water vapor on a small rocky body,” Benneke said.
“Hubble’s discovery opens the door to future exploration of these types of planets by the James Webb Space Telescope,” added Thomas Greene of NASA’s Ames Research Center. – With additional infrared sensors, it can see much more, including carbon-containing particles. Once we conduct a full inventory of the planet’s elements, we will be able to compare them with the star it orbits and understand how it was formed, he explained.
Main photo source: NASA/ESA/Leah Hustak/Ralf Crawford (STScI)