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One of the coldest planetary-mass objects ever directly imaged has been hiding something unusual in its atmosphere: salt clouds.
Known as the “Pink Planet,” GJ 504 b is a mysterious world orbiting a Sun-like star about 57 light-years from Earth. At roughly 25 times the mass of Jupiter, it lies near the uncertain boundary between giant planets and brown dwarfs. It is also so cold and faint that previous attempts to study its atmosphere from the ground were unsuccessful.
Now, JWST has captured the first direct spectrum of GJ 504 b. The observations revealed an atmosphere containing water vapor, methane, carbon dioxide, ammonia, hydrogen sulfide, and other molecules. When researchers modeled the spectrum, they found that clouds—particularly salt clouds—were essential to explaining what JWST observed.
Join host Moiya McTier and lead author Dr. Aneesh Baburaj (Northwestern University) to learn how astronomers separated the faint light of GJ 504 b from the glare of its host star, what salt clouds can tell us about cold planetary atmospheres, and why scientists still are not sure whether the Pink Planet formed like a planet or a star.
Thursday, August 6, 2026
2:30 p.m. PDT | 5:30 p.m. EDT | 21:30 UTC
Read the paper:
https://iopscience.iop.org/article/10.3847/1538-3881/ae6919
Read the Northwestern University story:
https://news.northwestern.edu/stories/2026/06/famous-pink-planet-harbors-a-salty-surprise
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