The Accretion Model
The accretion model argues that “planet formation begins when bits of dust present in a protostellar disk collide and cling together, forming agglomerations of solid material” (Laughlin 423). This process can take millions of years and is said to result in the formation of terrestrial and giant gas planets alike. The Core Accretion model has served as “a perfectly viable mechanism” of planet formation for many years (Lunine 462). However, because this is a gradual process, it has hit some turbulence with the discovery of these new exoplanets. Time is essential for the accretion model, because after “ten million years stars seem to lose their protoplanetary material”, and after this time has passed “formation of new planets must cease…because the disk mass is insufficient to make a core; if planets have not started to form, they never will” (Greaves 69). This posed a problem for scientists and the newly discovered planets because, “according to the pre-1995 planet formation theories, none of these objects were supposed to exist” (Santos, Benz and Mayor 252).