Astronomers using the James Webb Space Telescope have revealed an unusual chemical composition in the atmosphere of exoplanet GJ 504 b, known as the "Pink Planet." It turns out that its clouds contain salts, and the atmosphere itself differs significantly from anything scientists have seen before, Space.com reports.

What GJ 504 b is

The planet (or planetary companion) GJ 504 b was discovered in 2013. It orbits a Sun-like star at a distance of about 57 light-years from Earth. The object's mass is approximately 25 times that of Jupiter. With a temperature of around 290 °C and its characteristic pinkish hue, it is often called the "Pink Planet."

JWST's unexpected finding

New observations with JWST's instruments made it possible to obtain a detailed spectrum of the atmosphere. Scientists led by Anish Babulraj of Northwestern University (USA) detected water vapor, carbon dioxide, methane, and ammonia in it. However, the atmospheric models did not align until the researchers accounted for the presence of salt clouds in the deeper atmosphere.

Babulraj explained that when they accounted for the salt clouds, it suppressed the signals of molecules hidden deeper in the atmosphere, and the results became physically plausible, adding that this is the first time salt clouds have proven critical for explaining an object's spectrum.

Age and nature of the object

GJ 504 b is estimated to be between 2.5 and 4 billion years old. Like gas giants, such objects are born very hot and gradually cool down. At the same time, the "Pink Planet" turned out to be significantly richer in heavy elements (metals) than expected. This makes it impossible to definitively determine whether it is a gas giant or a brown dwarf (a "failed star").

Significance of the discovery

JWST observations have shown that even among "hot Jupiters," GJ 504 b stands out for its extreme nature. The new data help better understand how the atmospheres of such objects form and evolve, while also expanding our understanding of possible conditions on cold exoplanets.

In brief

The James Webb telescope has detected salt clouds in the atmosphere of exoplanet GJ 504 b (the "Pink Planet"), which had not been observed before. This helped explain the object's unusual spectrum. The planet has a temperature of about 290 °C and is 2.5–4 billion years old. The discovery highlights the uniqueness of GJ 504 b and shows just how complex the atmospheres of gas giants beyond the Solar System can be. The study was published in The Astronomical Journal.