Atmospheric composition and clouds detected on the planetary companion Gliese 504 b

Star system: 59 Virginis | Distance from the Sun: 57.4 light years

Gliese 504 b is a planetary-mass companion orbiting a distant star. Previously too faint for detailed study from the ground, this object has now been analyzed using the James Webb Space Telescope. The data reveal a complex atmosphere filled with various molecules and evidence of salt clouds, providing a rare look at the chemistry of a cool, directly imaged world.

Spectroscopic analysis—the process of breaking down light into a spectrum to identify chemical fingerprints—detected signatures of water, carbon monoxide, methane, carbon dioxide, ammonia, and hydrogen sulfide. These findings indicate an effective temperature of 564 Kelvin and suggest that the atmosphere is influenced by disequilibrium chemistry, where chemical reactions do not reach a simple balance.

Researchers achieved this by using advanced imaging techniques to separate the faint light of the planet from the glare of its host star. By modeling the atmospheric data, they determined the planet has a mass roughly 25 times that of Jupiter and an age between 2.5 and 4.0 billion years.

Comparison of the planet’s chemical abundances with its parent star shows higher levels of carbon, suggesting potential metal enrichment. This finding supports theories of planet-like formation, although stellar origins cannot be entirely ruled out at this time.

Key findings
- Detected molecular signatures of water, carbon monoxide, methane, carbon dioxide, ammonia, and hydrogen sulfide.
- Identified strong evidence of salt clouds and disequilibrium chemistry in the atmosphere.
- Estimated mass of 25.2 Jupiter masses and an age of 2.5 to 4.0 billion years.
- Confirmed an effective temperature of 564 Kelvin.
- Observed higher carbon levels compared to the host star, suggesting metal enrichment.

Scientific study

JWST-TST High Contrast: First Direct Spectroscopy of GJ 504 b reveals Clouds and Possible Metal Enrichment (external link)