James Webb Space Telescope Reveals Complex Weather on Wise 0855
It’s the first time we’ve been able to confirm that water clouds thin out and thicken on a nearby world,
said Brittany Miles, an astronomer at the University of Arizona. Located 7.5 light-years from Earth in the constellation Hydra, the celestial body has a mass between three and ten times that of Jupiter and a surface temperature of roughly -8 degrees Celsius. Neither a planet nor a star, Wise 0855 exists at the boundary where stellar fusion fails to ignite. A team led by Miles observed the object for 11 hours using the NIRSpec instrument on the James Webb Space Telescope, capturing a light spectrum every 15 minutes. This time-series spectroscopy allowed astronomers to track changes in atmospheric features over time, providing what researchers describe as the most detailed reconstruction of brown dwarf weather dynamics to date.
Two Distinct Processes Shape the Atmosphere of Wise 0855
Data from the observations reveal that two simultaneous processes govern the atmosphere of Wise 0855. At high altitudes, water clouds thicken and thin as the object rotates. Deeper inside the body, convective motions churn gases, transporting molecules upward from warmer subterranean layers.
Mark Marley, director of the Lunar and Planetary Laboratory at the University of Arizona and coadjutor on the study, compared the process to looking through a screen. Photons emitted from the interior pass through the atmosphere and scatter into space, creating a dynamic mosaic of warmer and cooler regions as different cloud covers rotate into view.
In addition to temperature variations linked to rotation, the NIRSpec instrument recorded an oscillatory signal tied to carbon monoxide and phosphine. Scientists attribute this rhythmic signal to internal heat driving gases toward the surface in a mechanism known as disequilibrium chemistry. While similar convective mixing occurs on Jupiter, researchers can now track these variations in real time, molecule by molecule, for an object outside the solar system.
Broader Implications for Gas Giants and Exoplanet Research
The findings, detailed in a study titled Water Cloud and Chemical Modulations in the Coldest Brown Dwarf accepted for publication in The Astronomical Journal, offer new frameworks for studying planetary atmospheres. The physical principles governing weather, cloud formation, and chemistry on Wise 0855 also apply to gas giants in our solar system and exoplanets discovered by the James Webb Space Telescope.
Even though brown dwarfs are not true planets, they show planet-like behaviors,
Miles noted. There is a continuous spectrum of behaviors among them, with no sharp dividing line.
Astronomers plan to use the James Webb Space Telescope for subsequent observations to refine measurements of the rotation period of Wise 0855 and investigate the three-dimensional dynamics of its atmosphere.
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