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JWST Finds First Salt Clouds on Cold Exoplanet

6/20/2026

Summary

Baburaj Detects Salt Clouds

U.S. astronomers led by astronomer Aneesh Baburaj used JWST to detect salt clouds in GJ504b’s atmosphere.
In a two-hour infrared observation that removed host-star glare, the planet—about 25 Jupiter masses and 550 °F—produced a spectrum showing methane, carbon dioxide, ammonia and salt clouds.
The finding provides the first evidence of salt clouds on a cold exoplanet, indicating a 500-700 °F weather type and confirming JWST’s capability for cold companions.

Summary

JWST Detects Clouds

JWST captured GJ504b’s faint infrared light in a two-hour observation, far shorter than earlier ground-based attempts.
Researchers removed host-star glare with advanced data-processing, yielding a clear spectrum that NASA-funded Northwestern University and Space Telescope Science Institute teams published in The Astronomical Journal and the Astrophysical Journal.
Model simulations showed that omitting salt clouds produced an implausible isothermal atmospheric layer, which vanished when the clouds were included.

History

Historical Context

NASA’s Hubble telescope announced in 2001 that sodium was seen in four transits of hot-Jupiter HD 209458 b, marking the first exoplanet atmosphere detection. Decades of transmission spectroscopy, including water and cloud findings, paved the way for Aneesh Baburaj’s Northwestern and STScI team to use JWST to identify salt-rich clouds on the massive companion GJ 504b, extending atmospheric profiling to cooler worlds.

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Baburaj Detects Salt Clouds

U.S. astronomers led by astronomer Aneesh Baburaj used JWST to detect salt clouds in GJ504b’s atmosphere.
In a two-hour infrared observation that removed host-star glare, the planet—about 25 Jupiter masses and 550 °F—produced a spectrum showing methane, carbon dioxide, ammonia and salt clouds.
The finding provides the first evidence of salt clouds on a cold exoplanet, indicating a 500-700 °F weather type and confirming JWST’s capability for cold companions.

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