  We hypothesise that planets are made by tidal downsizing of migrating giant
planet embryos. The proposed scheme for planet formation consists of these
steps: (i) a massive young protoplanetary disc fragments at R ~ several tens to
hundreds of AU on gaseous clumps with masses of a few Jupiter masses; (ii) the
clumps cool and contract, and simultaneously migrate closer in to the parent
star; (iii) as earlier suggested by Boss (1998), dust sediments inside the gas
clumps to form terrestrial mass solid cores; (iv) if the solid core becomes
more massive than ~ 10 Earth masses, a massive gas atmosphere collapses onto
the solid core; (v) when the gas clumps reach the inner few AU from the star,
tidal shear and evaporation due to stellar irradiation peel off the outer
metal-poor envelope of the clump. If tidal disruption occurs quickly, while the
system is still in stage (iii), a terrestrial planet core is left. If it
happens later, in stage (iv), a metal rich gas giant planet with a solid core
emerges from the envelope.
