  In its all-sky survey, Gaia will monitor astrometrically and photometrically
millions of main-sequence stars with sufficient sensitivity to brown dwarf
companions within a few AUs from their host stars and to transiting brown
dwarfs on very short periods, respectively. Furthermore, thousands of detected
ultra-cool dwarfs in the backyard of the Sun will have direct (absolute)
distance estimates from Gaia, and for these Gaia astrometry will be of
sufficient precision to reveal any orbiting companions with masses as low as
that of Jupiter. Gaia observations thus bear the potential for critical
contributions to many important questions in brown dwarfs astrophysics (how do
they form in isolation and as companions to stars? Can planets form around
them? What are their fundamental parameters such as ages, masses, and radii?
What is their atmospheric physics?), and their connection to stars and planets.
The full legacy potential of Gaia in the realm of brown dwarf science will be
realized when combined with other detection and characterization programs, both
from the ground and in space.
