Webb tracks changing water clouds beyond our Solar System

Astronomers using the James Webb Space Telescope have found evidence of water clouds changing thickness on a cold, free-floating world called WISE 0855. The team describes it as the first confirmation of such changes beyond our Solar System.

Roughly Jupiter’s size and more than seven light-years away, WISE 0855 is classified as a brown dwarf: an object that cannot sustain the nuclear reactions powering ordinary stars. Its estimated temperature is about minus 8 degrees Celsius.

A team led by Brittany Miles of the University of Arizona observed the object for 11 hours, recording its infrared light every 15 minutes. By separating that light into different wavelengths, researchers could identify the signatures of individual gases and distinguish effects that earlier brightness measurements had blurred together.

Comparisons with atmospheric models pointed to two processes. High in the atmosphere, different amounts of water-cloud cover rotated into view. Deeper down, heat-driven mixing brought gases such as carbon monoxide and phosphine upward, producing a separate changing signal.

Webb did not photograph individual clouds or storms. Researchers inferred the cloud properties by comparing the measured light with models. Even with that limitation, the observations offer a newly detailed view of weather on another world, and a chance to study atmospheric processes also at work on Jupiter.