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Water Vapor Detected in Atmosphere of Small Exoplanet GJ 9827d

Despite the presence of water, the exoplanet's high temperatures make it unlikely to host life, with further observations planned using the Webb telescope.

This is an artist's concept of the exoplanet GJ 9827d, the smallest exoplanet where water vapor has been detected in the atmosphere. The planet could be an example of potential planets with water-rich atmospheres elsewhere in our galaxy. With only about twice Earth's diameter, the planet orbits the red dwarf star GJ 9827. Two inner planets in the system are on the left. The background stars are plotted as they would be seen to the unaided eye looking back toward our Sun. The Sun is too faint to be seen. The blue star at upper right is Regulus; the yellow star at center bottom is Denebola; and the blue star at bottom right is Spica. The constellation Leo is on the left, and Virgo is on the right. Both constellations are distorted from our Earth-bound view from 97 light-years away.

Overview

  • Astronomers using the Hubble Space Telescope have detected water molecules in the atmosphere of a small exoplanet named GJ 9827d, making it the smallest exoplanet found to have water vapor in its atmosphere.
  • The planet, which is about twice Earth’s diameter and 97 light-years from Earth, is unlikely to host any type of life due to its high temperatures that would turn a water-rich atmosphere into scorching steam.
  • The research team is unsure whether Hubble picked up on water vapor traces within a puffy, hydrogen-rich atmosphere or the planet has a water-rich atmosphere because the host star evaporated GJ 9827d’s original hydrogen and helium atmosphere.
  • The exoplanet completes a single orbit around its host star every 6.2 days, and was observed during 11 transits, or times when the planet crossed in front of its star during orbit, over three years.
  • Astronomers have already observed GJ 9827d with the Webb telescope to search for water and other types of molecules, and that data will be shared in the future.