Closest Brown Dwarf To Earth Revealed To Have Stripes

Artist impression of what Luhman 16 B might look like. Daniel Apai

New observations of Luhman 16 B, the closest brown dwarf to Earth, suggests that its atmosphere is dominated by high-speed global winds, which alters clouds distribution and gives the object a stripey appearance. This first-of-a-kind study of the atmosphere is reported in The Astrophysical Journal.

Brown dwarfs are odd astronomical beasts. Some of them are smaller than Jupiter and Saturn, but they are tens of times more massive. However, that’s not massive enough to be fully-fledged stars, hence why these stellar bodies are often called failed stars.

These objects are hot when they form and gradually cool, and are expected to have active atmospheres. But it wasn’t exactly clear if the atmospheres would have bands or vortices or be somewhat different.

"We wondered, do brown dwarfs look like Jupiter, with its regular belts and bands shaped by large, parallel, longitudinal jets, or will they be dominated by an ever-changing pattern of gigantic storms known as vortices like those found on Jupiter's poles?" lead author Professor Daniel Apai, from the University of Arizona, said in a statement.

Using a new algorithm and data from NASA’s Transiting Exoplanet Survey Satellite (TESS), the team delivered what no other telescope is currently capable of achieving: clear evidence that this brown dwarf is covered in stripes parallel to the equator, polar regions dominated by vast vortices, and high-speed winds that churn the atmosphere redistributing the heat from the failed star interior.

"Wind patterns and large-scale atmospheric circulation often have profound effects on planetary atmospheres, from Earth's climate to Jupiter's appearance, and now we know that such large-scale atmospheric jets also shape brown dwarf atmospheres," added Apai. "Knowing how the winds blow and redistribute heat in one of the best-studied and closest brown dwarfs helps us to understand the climates, temperature extremes and evolution of brown dwarfs in general."


TESS is designed to discover new exoplanets by carefully monitoring the change in brightness of thousands of stars. Given that the Luhman 16 system is just 6.56 light-years away, TESS's keen eye could be employed to spot atmospheric science.

"No telescope is large enough to provide detailed images of planets or brown dwarfs," Apai explained. "But by measuring how the brightness of these rotating objects changes over time, it is possible to create crude maps of their atmospheres – a technique that, in the future, could also be used to map Earthlike planets in other solar systems that might otherwise be hard to see."

Luhman 16 B weighs an equivalent of 28 times the mass of Jupiter, and is in a binary system with a fellow brown dwarf (Luhman 16 A) that weighs 34 times the mass of Jupiter.


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