Webb sees water clouds thickening and thinning on a cold world 7.5 light-years away
Using the James Webb Space Telescope, astronomers watched water clouds grow thicker and thinner on WISE 0855, the coldest known brown dwarf, the first direct confirmation of changing water clouds beyond the solar system.
By Diego Callegari, Editor
· 1 min read
Source: University of Arizona Lunar and Planetary Laboratory ↗
Astronomers using the James Webb Space Telescope have seen water clouds growing thicker and thinner on WISE 0855, the coldest known brown dwarf, 7.5 light-years from Earth, the University of Arizona reported. It is the first direct confirmation of changing water clouds on a body outside our solar system. The study is published in The Astrophysical Journal.
A world colder than Earth's surface
Brown dwarfs are too massive to be planets but too small to ignite like stars, and glow faintly with leftover heat. WISE 0855 sits at about 265 kelvin, around minus 8°C, colder than Earth's average surface temperature. At about twice Jupiter's mass and nearly the same size, it behaves much like a free-floating giant planet.
Eleven hours of spectra, one every 15 minutes
A team led by Brittany Miles of the University of Arizona's Steward Observatory watched WISE 0855 for 11 hours, recording a spectrum every 15 minutes. As the object rotated, patches with different cloud cover and temperature turned into view. The data showed high-altitude water clouds changing thickness, as well as gases being dredged up from deep layers by convection, the same process seen on Jupiter.
“This is the first time we've been able to confirm that water clouds are becoming thinner and thicker on a nearby world.” — Brittany Miles, Steward Observatory, University of Arizona
Before Webb, astronomers had only broadband brightness measurements, which mixed the effects of clouds, chemistry and temperature. Webb's spectrograph could separate them, molecule by molecule.
Lessons for giant exoplanets
The researchers say the same physics of convection, clouds and chemistry that shapes Jupiter appears to work here, which should help astronomers interpret giant exoplanets that Webb is beginning to study. Miles plans more observations to map the object's rotation and 3D weather. The list of known planets keeps growing too: NASA's TESS mission recently passed 1,000 confirmed exoplanets.
Sources
- University of Arizona Lunar and Planetary Laboratory · lpl.arizona.edu
How we choose and verify sources: editorial policy.
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