The James Webb Space Telescope (JWST) has made a groundbreaking discovery, identifying the first known 'steam world' exoplanet, GJ 9827 d, located approximately 100 light-years from Earth. This planet, which is about twice the size and three times the mass of Earth, is enveloped in a thick atmosphere predominantly composed of water vapor.
Team member Eshan Raul from the University of Wisconsin-Madison remarked, "This is the first time we're ever seeing something like this. The planet appears to be made mostly of hot water vapor, making it something we're calling a 'steam world.'" While GJ 9827 d is not suitable for life as we know it, its discovery provides valuable insights into the characteristics of small exoplanets that may be habitable.
Led by Caroline Piaulet-Ghorayeb from the University of Montréal, the research team utilized transmission spectroscopy to analyze the planet's atmosphere. This method reveals the presence of specific elements by identifying gaps in the light spectrum as it passes through the atmosphere. Unlike many previously studied exoplanets, GJ 9827 d's atmosphere is rich in heavy molecules, akin to terrestrial planets in our solar system.
Discovered by the Kepler space telescope in 2017, GJ 9827 d orbits its host star at a distance of just 5.2 million miles, completing an orbit in a little over six Earth days. The JWST's advanced capabilities allowed researchers to confirm the presence of substantial water vapor, a significant leap from earlier findings by the Hubble Space Telescope.
Raul expressed excitement about the potential for discovering more steam worlds, stating, "If these are real, it really makes you wonder what else could be out there." The team's findings were published on October 4 in the Astrophysical Journal Letters, marking a significant milestone in the study of exoplanets.