Astronomers tracking the coldest known brown dwarf have captured direct evidence of water clouds thickening and thinning in real time, revealing dynamic weather patterns on a sunless celestial body just 7,5 light-years from Earth.
Monitoring WISE 0855 with the James Webb Space Telescope
Using the James Webb Space Telescope (JWST), a research team led by Brittany Miles of the Stewart Observatory at the University of Arizona monitored the object known as WISE 0855 for 11 consecutive hours. Every 15 minutes, the space telescope recorded the spectrum of light emitted from the frigid object. This approach allowed scientists to separate the shifting signals of water clouds from the signals of gases transported at higher altitudes by heat in the atmosphere.
Before the James Webb Space Telescope became operational, researchers relied primarily on optical measurements that struggled to isolate individual variables such as cloud density, chemical composition, and temperature. The new spectral data confirm that water clouds in the upper atmosphere of WISE 0855 undergo continuous cycles of condensation and dispersion, mimicking familiar weather phenomena observed on gas giants within our own solar system.
Brittany Miles stated that this is the first time they have been able to confirm that water clouds are thinning and thickening on a planet so close to us.
Probing the Boundary Between Planets and Stars
Brown dwarfs occupy a distinct astronomical gray area. They possess greater mass than typical planets but lack the internal pressure required to sustain stable hydrogen fusion in their cores like normal stars. Instead of generating energy through nuclear reactions, objects like WISE 0855 slowly radiate away the leftover heat from their formation.
WISE 0855 carries roughly twice the mass of Jupiter while sharing similar physical dimensions. With a temperature hovering around -8 degrees Celsius, it ranks among the coldest atmospheric environments accessible for detailed observation. Because the body drifts through space without a host star, its internal heat drives vigorous convection, forcing warm material upward while cooler matter sinks.
Atmospheric Updrafts and Chemical Disequilibrium
As WISE 0855 rotates, spectral signatures associated with carbon monoxide and phosphine reveal repetitive wave patterns. These fluctuations indicate that warm gases from deep within the interior surge toward the upper atmosphere in a process comparable to boiling soup. This rapid transport of matter outpaces chemical equilibrium, creating a state known as chemical disequilibrium.
While similar convective processes have been documented on Jupiter and other brown dwarfs, the latest observations provide the ability to track changes over time in individual molecules. The findings establish that fundamental physical laws governing heat transport and cloud formation operate consistently across vastly different substellar worlds, offering a framework for analyzing massive exoplanets detected by modern observatories.
