On October 11, 2024, scientists utilizing the James Webb Space Telescope announced the discovery of an exoplanet named GJ 9827 d, located approximately 100 light-years from Earth in the constellation Pisces. This planet is notable for its atmosphere, which is almost entirely composed of water vapor, marking the first direct evidence of a 'steam world.'
GJ 9827 d is a rocky super-Earth, roughly double the size of Earth, with an estimated surface temperature of 660 degrees Fahrenheit. Researchers believe that the planet's extreme heat results in a thick, water-rich atmosphere, devoid of ice or flowing water. This discovery challenges previous theories about the existence of such planets in the universe.
The research team, led by doctoral student Caroline Piaulet-Ghorayeb from the University of Montréal, utilized transmission spectroscopy to analyze the planet's atmosphere. This technique involves observing starlight filtered through the atmosphere of the exoplanet to determine its molecular composition. The findings were published in the Astrophysical Journal Letters.
This discovery is significant as it represents the first confirmed case of an exoplanet atmosphere where hydrogen is not the dominant component. The James Webb Space Telescope will continue to study GJ 9827 d, contributing to a broader understanding of rocky worlds outside our solar system and the potential for discovering habitable exoplanets in the future.