A massive gas giant circling a faraway star similar to the Sun has offered researchers fresh insights into weather patterns on some of the coldest exoplanets known. Data from the James Webb Space Telescope allowed scientists to detect signs of salt-rich clouds in the atmosphere of GJ 504 b, a large world nicknamed the Pink Planet for its rosy color. The finding, detailed in a study published in the Astronomical Journal, expands knowledge of atmospheres outside our solar system. Discovered over ten years ago, the object had been hard to examine because of its faint light and cool temperature. Earlier efforts yielded little information, but the telescope’s capabilities produced a detailed spectrum within hours, showing an atmosphere more intricate than expected. Located roughly 57 light-years away, the body has a mass about 25 times that of Jupiter and sits near the divide between giant planets and brown dwarfs. Astronomers still debate its formation process. Its pink tint earned the nickname that has remained in use. With an atmospheric temperature near 564 Kelvin, or about 290 degrees Celsius, it ranks among the coldest planetary-mass companions imaged directly. Most such worlds are much hotter. Spectroscopy identified gases including water vapor, methane, carbon dioxide, ammonia, and hydrogen sulfide. Models initially failed to match the data until cloud layers were added. The best fit came from clouds made of compounds such as potassium chloride and zinc sulphide. These mineral particles, unlike water-based clouds on Earth, form in cooler giant-planet conditions. Adding the clouds resolved mismatches in the models and muted deeper molecular signals, aligning results with expectations for a cold giant world. The observations also indicated higher levels of heavy elements than in the host star.
