  Recent observations of exoplanets by direct imaging, reveal that giant
planets orbit at a few dozens to more than a hundred of AU from their central
star. The question of the origin of these planets challenges the standard
theories of planet formation. We propose a new way of obtaining such far
planets, by outward migration of a pair of planets formed in the 10 AU region.
Two giant planets in mean motion resonance in a common gap in the
protoplanetary disk migrate outwards, if the inner one is significantly more
massive than the outer one. Using hydrodynamical simulations, we show that
their semi major axes can increase by almost one order of magnitude. In a
flared disk, the pair of planets should reach an asymptotic radius. This
mechanism could account for the presence of Fomalhaut b ; then, a second, more
massive planet, should be orbiting Fomalhaut at about 75 AU.
