One of astronomy’s greatest frustrations is the sheer distance to even the nearest objects. We want to know what exoplanets actually look like and study sunspots on other stars. Unfortunately, the light-years of emptiness between our solar system and its nearest neighbors make directly seeing details generally impossible. Nevertheless, we do the best we can, and sometimes, we’re able to figure out details through logical deductions that would make Sherlock Holmes proud.
One of my favorite mysteries involves brown dwarfs. These objects are roughly the same diameter as Jupiter but pack in as much as 80 to 100 times its mass and are capable of undergoing short periods of nuclear fusion as they burn heavy hydrogen. Because they are very small and very faint, they are very hard to observe, and basic questions like do they have hot and cool bands like Jupiter or convection cells and spots like the Sun… well, we haven’t been able to answer those questions. At least until now.
A new paper in The Astrophysical Journal by Faniel Apai, Domenico Nardiello, and Luigi Bedin describes changes in light from the brown dwarf Luhman 16B that were recorded over 100 rotations.
If the stars have spots, they will vary in brightness more significantly than if they have stripes. Their data shows that this brown dwarf’s changes in brightness during rotation are consistent with it being banded like Jupiter.
According to Apai: 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. 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.
The technique used in this study will be used to study other brown dwarfs as we look to understand these weird objects that bridge between gas giants and red dwarf stars.
“TESS Observations of the Luhman 16 AB Brown Dwarf System: Rotational Periods, Lightcurve Evolution, and Zonal Circulation,” Dániel Apai, Domenico Nardiello, and Luigi R. Bedin, 2021 January 7, The Astrophysical Journal