Astronomers using the James Webb Space Telescope have confirmed the first shifting water clouds on a cold brown dwarf located 7.5 light-years from Earth. The discovery, led by University of Arizona researchers, tracked eleven hours of continuous infrared data to separate cloud thickness changes from deep atmospheric gases.
Telescope Tracks Weather on WISE 0855
Researchers focused on WISE 0855, recognized as the coldest known brown dwarf, during an 11-hour monitoring campaign. The James Webb Space Telescope recorded a new infrared spectrum every 15 minutes as the object rotated, capturing how different atmospheric regions drifted into view.
The research paper is published in The Astrophysical Journal and is available on the arXiv preprint server. A team led by Brittany Miles of the Steward Observatory at the University of Arizona authored the work, which addresses unique weather patterns on a brown dwarf. This object floats through space without a host star. The observations covered wavelengths from 2.87 to 5.27 micrometers, collecting forty-four spectra across approximately eleven hours on December 2, 2023, using the Near-Infrared Spectrograph. Spitzer monitoring also showed that its brightness varied, but the new advance follows a detailed spectrum repeatedly.
Distinguishing temperature shifts from cloud changes or chemical variations proved impossible with older instruments. By deploying the telescope’s medium-resolution spectrometer, the team untangled those overlapping factors by analyzing how individual wavelengths behaved over time.
Team Separates Clouds from Deep Gases
Led by Brittany Miles of the University of Arizona’s Steward Observatory, the research team used computer models to interpret the spectral variations. The data confirmed that water clouds at high altitudes become denser or thinner as the roughly Jupiter-sized object turns on its axis.
These chemical signatures point to vigorous internal mixing, where heat from deeper layers pushes gases upward into colder regions.
James Webb Space Telescope Helps Researchers Map Complex Atmospheres
Brown dwarfs occupy a transitional space between massive planets and stars, lacking the hydrogen mass required to ignite nuclear fusion.
As the James Webb Space Telescope expands its surveys of distant worlds, the models refined through these continuous observations will help researchers map complex atmospheres across the galaxy.