Scientists Discover Bands Of Clouds Streaking Across A Brown Dwarf

Astronomers have detected something interesting on the surface of a cool star-like body known as a brown dwarf. The team of astronomers has identified what appear to be bands of clouds that are streaking across the surface of the brown dwarf. Those cloud bands are said to resemble clouds that stripe the surface of Jupiter and were discovered using a technique called polarimetry.The technique is said to work in the same way that polarized sunglasses can block the glare of sunlight. One researcher, Robert A Millikan, says that he thinks of polarimetric instruments as "an astronomer's polarized sunglasses." He says that rather than trying to block glare, the astronomers want to measure it.

Evidence of bands of clouds on brown dwarf stars have been seen before, but this discovery represents the first-time cloud features have been inferred using polarimetry technique. The brown dwarf that the astronomers observed in the study is called Luhman 16A, which is part of a binary pair that represents the closest known binary brown dwarf system to our solar system. The system is 6.5 light-years away from our solar system.

Previous observations made with the NASA Spicer Space Telescope found that three other brown dwarfs had signs of cloud banding, and prior studies of the partner brown dwarf to Luhman 16A called Luhman 16B have inferred the presence of large cloud patches. All of the previous measurements looked at how the brightness of the objects varied over time rather than measuring polarized light.

The new study uses the VLT's NaCo instrument study polarized light from both of the Luhman brown dwarfs. The researchers note they can't image the brown dwarf itself. Their measurements are of the amount of polarized light coming from it that allows them to infer the presence of cloud bands using sophisticated atmospheric modeling. They are unable to specify exactly how many bands of clouds are rotating around the brown dwarf, but their models suggest two.