Of these, only a handful are bright enough and close enough to be studied for weather. Tinney s team is leading Southern Hemisphere attempts to learn more about brown dwarfs. They are very faint, and extremely difficult to detect, and for Tinney and Tolley to have noted surface changes is remarkable. Brown dwarfs never made it as stars, being too small to light up their nuclear furnaces. Instead, they just smoulder away in space at temperatures below 2000 degrees less than a third that of a typical star like the sun.
Proper stars are so hot that their surfaces are a completely smooth mix of vapourised material.
But the outer layers of brown dwarfs are cool enough for chemicals to rain out as smoke-like particles. Tinney said, Brown dwarfs are too small and far away to see the clouds. We detected them indirectly through the effects they have on the brown dwarf s atmosphere. We looked for a changing pattern of chemistry in the atmosphere of one brown dwarf, called LP944-20, as it rotated. With a special instrument developed by the AAT, called the Taurus Tuneable Filter, Tinney and Tolley were able to tune into a very narrow wavelength band and accurately measure tiny fluctuations.