Brown dwarfs are the coolest class of stellar objects known to date. Our present perception is that brown dwarfs follow the principles of star formation, and that brown dwarfs share many characteristics with planets. Being the darkest and lowest mass stars known makes brown dwarfs also the coolest stars known. This has profound implication for their spectral fingerprints. Brown dwarfs cover a range of effective temperatures which cause brown dwarfs atmospheres to be a sequence that gradually changes from a M-dwarf-like spectrum into a planet-like spectrum. This further implies that below an effective temperature of $$\lesssim $$≲2,800 K, clouds form already in atmospheres of objects marking the boundary between M-Dwarfs and brown dwarfs. Recent developments have sparked the interest in plasma processes in such very cool atmospheres: sporadic and quiescent radio emission has been observed in combination with decaying X-ray activity indicators across the fully convective boundary.

中文翻译：

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棕矮星的大气层

棕矮星是迄今为止已知的最酷的一类恒星。我们目前的看法是，棕矮星遵循恒星形成的原则，而且棕矮星与行星有许多共同特征。作为已知最暗、质量最低的恒星，棕矮星也是已知的最冷恒星。这对他们的光谱指纹有着深远的影响。褐矮星覆盖了一系列有效温度，这导致褐矮星大气是一个序列，从类似 M 矮星的光谱逐渐转变为类似行星的光谱。这进一步意味着在低于 $$\lesssim $$≲ 2,800 K 的有效温度下，云已经形成在标志着 M 矮星和棕矮星之间边界的物体的大气中。最近的发展激发了人们对这种非常凉爽的气氛中的等离子体工艺的兴趣：