Caltech: Bands of Clouds Swirl Across Brown Dwarf's Surface

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Bands of Clouds Swirl Across Brown Dwarf's Surface
California Institute of Technology | 2020 May 05

"Astronomers sunglasses" used to measure cloud features on cool cosmic orb

Astronomers have found evidence for a striped pattern of clouds on the brown dwarf called Luhman 16A, as illustrated here in this artist's concept. The bands of clouds were inferred using a technique called polarimetry, in which polarized light is measured from an astrophysical object much like polarized sunglasses are used to block out glare. This is the first time that polarimetry has been used to measure cloud patterns on a brown dwarf. Credit: Caltech/R. Hurt (IPAC)

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Astronomers have detected what appear to be bands of clouds streaking across the surface of a cool star-like body known as a brown dwarf. The bands, resembling those that stripe the surface of Jupiter, were discovered using polarimetry, a technique that works in the same way that polarized sunglasses block out the glare of sunlight. ...

While evidence for bands of clouds on brown dwarfs has been seen before, this discovery represents the first time that these features have been inferred using the polarimetry technique. ...

The brown dwarf in the new study, called Luhman 16A, is part of a pair that together represents the closest known binary brown dwarf system to our solar system, lying at a distance of 6.5 light-years away. Discovered by NASA's Wide-field Infrared Survey Explorer (WISE) in 2013, each orb weighs roughly 30 times the mass of Jupiter. Brown dwarfs form from collapsing clouds of gas in a similar fashion to stars but they lack enough mass to ultimately ignite and shine with starlight.

Previous observations with NASA's Spitzer Space Telescope found that three other brown dwarfs had signs of cloud banding, and previous studies of the partner brown dwarf to Luhman 16A, called Luhman 16B, have inferred the presence of large cloud patches. But all of these previous measurements looked at how the brightness of the objects varied over time and did not measure polarized light. In the new study, the VLT's NaCo instrument was used to study polarized light from both of the Luhman brown dwarfs. ...

Astronomers Find Jupiter-like Cloud Bands on Closest Brown Dwarf
NASA | STScI | HubbleSite | 2020 May 05

Detection of Polarization Due to Cloud Bands in the Nearby
Luhman 16 Brown Dwarf Binary ~ Maxwell Millar-Blanchaer et al

• Astrophysical Journal 894(1):42 (2020 May 01) DOI: 10.3847/1538-4357/ab6ef2