Scientific Rationale

Brown dwarfs have emerged as new objects in observational astronomy in the last few years. Our knowledge of the solar neighborhood, star and planet formation processes, galactic evolution and dynamics, is incomplete until we find many Brown Dwarfs and learn about their statistics. Imaging surveys have revealed numerous Brown Dwarfs close to the Sun, and in nearby clusters and associations. Many of the new objects have properties different to those of stars. The coolest Brown Dwarfs have optical spectra dominated by resonance lines of alkali elements, and near-infrared spectra dominated by methane and water absorption. While Brown Dwarfs have unique properties, they are also connected with other important areas of astronomy such as the missing mass, galactic structure, star formation and planet formation.

Deep surveys for Brown Dwarfs in star-forming regions and young open clusters are finding extremely low-mass objects. The luminosities of these faint free-floaters overlap with those expected for recently formed giant planets. These discoveries are opening challenging new questions about the origin and evolution of Brown Dwarfs and their relation to star and planet formation. High-resolution imaging and spectroscopy are being applied to the search for Brown Dwarf companions to stars, and for Brown Dwarf binaries. The statistics of binary systems as a function of age and mass will constrain formation scenarios. Other current problems in Brown Dwarf research include:

1. Completing the census of objects in the solar vicinity. Some of our nearest neighbors may be old Brown Dwarfs that have cooled to very faint luminosities.
2. Investigating the scale height of Brown Dwarfs in the Milky Way
3. Searching for halo Brown Dwarfs which may contribute to the dark matter in the Galaxy
4. Classification schemes for Brown Dwarfs
5. Temperature, gravity and chemical composition determinations
6. Detailed analysis of Brown Dwarf spectra to extract physical information about their atmospheres and interiors, one of the main problems is the lack of good molecular data
7. Activity and variability due to magnetic fields and weather (dust formation and condensation)

Progress in this new field of astrophysics will come from larger surveys for Brown Dwarfs, spectroscopic follow-up, multiwavelength campaigns to search for variability, and theoretical efforts to understand the origins, evolution and properties of Brown Dwarfs . The Symposium would provide an excellent opportunity to elaborate a strategy, based on the acquired experience, to plan future surveys best fitted to fulfill the needs, and to coordinate follow-up observations with the new large ground-based and space telescopes.