ESO’s VLT (Very Large Telescope) allowed to create for the first time a map of the climate on the surface of a brown dwarf called Luhman 16B, formally known as WISE J104915.57-531906.1B. It’s part of a binary system together with another brown dwarf at a distance of about 6.5 light years from the Earth. That makes them the third closest star system to Earth after that of Alpha Centauri and Barnard’s Star. Despite their relative closeness, these brown dwarfs have been discovered only in early 2013 by astronomer Kevin Luhman, hence their informal name, because of their very faint light.
The Luhman 16 binary system was discovered using images taken by NASA’s WISE (Wide-field Infrared Survey Explorer) space telescope during its original mission, which ended in February 2011 after the exhaustion of the hydrogen used to keep some instruments for infrared investigation at temperatures near absolute zero.
The analysis of the images taken by the WISE telescope has been going on even after the end of its original mission and allowed the discovery of the Luhman 16 binary system. The two brown dwarfs that compose it are substellar objects halfway between stars and planets. Their mass is too low to ignite hydrogen fusion in their cores thus emit only a very faint infrared light thanks to the energy produced by their slow contraction.
Luhman 16B immediately showed changes in its brightness indicating the particular characteristics of its surface. The astronomers used the VLT’s CRIRES (Cryogenic InfraRed Echelle Spectrograph high-resolution) instrument, a sophisticated infrared spectrograph, to create a map of the climate of this brown dwarf.
Brown dwarfs are in many ways more similar to gals giant planets than to stars so the study of their atmosphere provides information useful in the study of the biggest and hottest exoplanets. Studying a brown dwarf such as Luhman 16B is simpler because it’s easier to observe it than a planet that is close to its star whose light will interfere with the observations.
In general, the study of brown dwarfs weather helps to develop climate models of other solar systems. That’s because certain patterns are the same or at least similar so the models developed using information collected on Luhman 16B can be easily adapted to places many light years away. Maybe they’ll be useful even in the development of Earth’s meteorology.
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