What revisions to the theory of planet formation have astronomers had to make as a result of the discovery of exoplanets?

1.state2.trash3.the earth

Ok what do you need with

Answer(a)   the matererials that are in contact, the two materials and the nature of their surfaces/// (b)/// the force pushing the two surfaces together, pushing the surfaces together causes the more of the asperities to come together and increases the surface area in contact with each other