Scientists using ESO's Very Large Telescope (VLT) have learned what the weather is like on the surface of one of the objects in the system Luhman 16AB.
Brown dwarfs are substellar bodies more massive than planets but not massive enough to initiate the sustained hydrogen fusion that powers self-luminous stars.1, 2 They are born hot and slowly cool as they age. Once they cool below about 2,300 degrees kelvin, liquid or crystalline particles composed of calcium aluminates, silicates and iron condense into atmospheric ‘dust’3, 4, which disappears at still cooler temperatures (around 1,300 degrees kelvin)5, 6. Models to explain this dust dispersal include both an abrupt sinking of the entire cloud deck into the deep, unobservable atmosphere5, 7 and breakup of the cloud into scattered patches6, 8 (as seen on Jupiter and Saturn9). However, hitherto observations of brown dwarfs have been limited to globally integrated measurements10, which can reveal surface inhomogeneities but cannot unambiguously resolve surface features11. Astronomers from Germany, France and the United Kingdom now report a two-dimensional map of a brown dwarf’s surface that allows identification of large-scale bright and dark features, indicative of patchy clouds. Monitoring suggests that the characteristic timescale for the evolution of global weather patterns is approximately one day.
The cryogenic high-resolution infrared echelle spectrograph (CRIRES) on the telescope allowed the team to see the changing brightness as Luhman 16B rotated and whether dark and light features were moving away from, or towards the observer.
By combining all the results they could recreate a map of the dark and light patches of the surface. “Previous observations suggested that brown dwarfs might have mottled surfaces, but now we can actually map them,” said Dr. Ian Crossfield of Max Planck Institute for Astronomy in Heidelberg. “Soon, we will be able to watch cloud patterns form, evolve, and dissipate on this brown dwarf – eventually, exometeorologists may be able to predict whether a visitor to Luhman 16B could expect clear or cloudy skies,” he said.
Via Dr. Stefan Gruenwald