JWST Reveals Salt Clouds in the Atmosphere of the ‘Pink Planet’ GJ 504b

The James Webb Space Telescope (JWST) has successfully decoded the spectrum of the coldest known exoplanet-like object, GJ 504b. This object in space has a salty atmosphere and is nicknamed the “Pink Planet” because of its pinkish color. It orbits a sun-like star 57 light-years away and could be either a giant planet or a failed star. Such results were obtained in just two hours of observing with the help of JWST.

How JWST Cracked the Code

Published June 18 in The Astronomical Journal, the study—led by Northwestern postdoctoral researcher Aneesh Baburaj—used JWST's NIRSpec instrument to isolate GJ 504b's faint glow from its host star's glare, something ground telescopes had failed to do for years. The spectrum revealed water vapour, carbon dioxide, methane, and ammonia, but standard models couldn't reproduce it. After testing three cloud types, the team found deep salt clouds fit best, muting signals from molecules lower in the atmosphere. This also indicated an age of 2.5 to 4 billion years, explaining its cool 550°F temperature.

Planet, Star, or Something Between?

While the nature of its spectrum was settled, the classification of GJ 504b is still under discussion. According to the findings obtained through the use of JWST, the object is highly enriched in heavy elements, making it hard to draw a line between the planet having formed from the circumstellar disk and the brown dwarf having formed in a similar way to stars. Baburaj adds that the cloud model method can be used to describe other cold and dim objects, including those with Jupiter-like ammonia clouds that are not bright enough to be detected at the moment.