Astronomers using the James Webb Space Telescope discovered salty clouds surrounding the exoplanet GJ 504b, also known as the “Pink Planet” [1, 2].
The discovery challenges existing models of planetary atmospheres by revealing chemical compositions that scientists did not expect to find on such a cold object. This finding provides new insights into how planetary-mass companions form and evolve in deep space.
Led by astrophysicist Aneesh Baburaj of Northwestern University, the research team used spectroscopic analysis to study the atmosphere [1, 3]. The data revealed absorption features consistent with sodium-chloride particles, which indicates the presence of salt clouds [1, 3].
"We were very surprised," Baburaj said [1].
Located about 57 light-years from Earth in the constellation of Virgo, GJ 504b was first discovered in 2013 [1, 2]. While often referred to as a planet, the object is technically classified as a planetary-mass companion [1].
Baburaj said that the presence of these specific particles was an anomaly given the environment. "The clouds are composed of salt particles, something we didn’t expect on such a cold, planetary-mass companion," Baburaj said [2].
The team's findings, announced in June 2024, highlight the precision of the James Webb Space Telescope in detecting specific chemical signatures across vast distances [1, 2]. By identifying these salts, researchers can better understand the temperature and pressure gradients of the atmosphere surrounding the pink-hued world.
“"We were very surprised."”
The detection of sodium-chloride on GJ 504b suggests that the chemical diversity of exoplanets is broader than previously theorized. Because salt clouds were unexpected for a body of this temperature, this discovery may force astronomers to revise the atmospheric chemistry models used to categorize planetary-mass companions and cold gas giants.
