James Webb Space Telescope detects changing water clouds on brown dwarf

Astronomers using the James Webb Space Telescope (JWST) have detected changing water clouds on WISE 0855, a cold brown dwarf located approximately 7.5 light-years from Earth. The object, which is roughly the size of Jupiter but possesses about twice its mass, is one of the coldest brown dwarfs ever identified, with a temperature of approximately -8 degrees Celsius (265 Kelvin).

A research team led by Brittany Miles at the University of Arizona’s Steward Observatory monitored the object for 11 hours, measuring light every 15 minutes. Using the JWST’s NIRSpec instrument to analyze infrared light variations, scientists confirmed that the water clouds fluctuate in thickness as the object rotates.

The study suggests two primary drivers for these atmospheric changes: the movement of high-altitude water clouds caused by the object's rotation, and internal heat that drives convection, pushing gases like carbon monoxide and phosphine upward. This discovery demonstrates that active weather patterns similar to those seen on gas giants like Jupiter also occur on drifting, sub-stellar objects.