Astronomers have recently identified the presence of large cloud bands resembling those of Jupiter in the atmosphere of a brown dwarf.
Between the planets and the stars are positioned intermediate objects: the brown dwarfs. We know that these objects are formed in the same way as stars, following the collapse under their own gravity of pockets of clouds of gas and dust. But, while the stars end up accumulating enough mass to allow thermonuclear reactions, thus allowing them to “shine”, the brown dwarfs do not go that far. On the other hand, they still remain more massive than planets (between ten and eighty times the mass of Jupiter).
However, these objects are still very enigmatic. In an attempt to learn more, researchers at Caltech recently focused on studying their atmosphere.
Two large cloud bands
To do this, they used the Very Large Telescope (VLT) in Chile to confirm or not the presence of clouds in the envelope of Luhman 16A, the brown dwarf closest to Earth. This object evolves with a binary companion – Luhman 16B – at 6.5 light-years.
To study the object, the team used a technique called polarimetry which, roughly speaking, aims to measure the polarization of light, a phenomenon that occurs when light waves vibrate in a single plane.
In this case, the light radiating on the surface of the brown dwarf disperses the molecules in the atmosphere, polarizing it in a certain way. Polarimetric instruments can then tell whether this polarization is uniform (or not) over the entire atmospheric surface.
Concerning the object that interests us, Luhman 16A, the researchers noticed that certain signals were stronger in certain parts than in others, suggesting the presence of cloud bands. Thanks to computer simulations modeling the formation of these structures, it emerged that the program that best corresponded to the light imprint of the brown dwarf involved the presence of two large cloud bands.
This is the first time that the polarimetry technique has been used to understand the properties of clouds outside the solar system. And, according to this work, the approach seems to work well.
Ultimately, according to the researchers, the study of polarized light by future powerful telescopes could also help us better understand the atmospheres and, ultimately, the habitability of exoplanets.
