Brown Dwarfs

After a discussion of the physical processes in brown dwarfs, we present a complete, precise definition of brown dwarfs and of planets inspired by the internal physics of objects between 0.1 and 0.001 M_sun. We discuss observational techniques for characterizing low-luminosity objects as brown dwarfs, including the use of the lithium test and cooling curves. A brief history of the search for brown dwarfs leads to a detailed review of known isolated brown dwarfs with emphasis on those in the Pleiades star cluster. We also discuss brown dwarf companions to nearby stars, paying particular attention to Gliese 229B, the only known cool brown dwarf.