" ▁is ▁that ▁the ▁terrest ri als ▁formed ▁in ▁a ▁disc ▁of ▁gas ▁still ▁not ▁exp elled ▁by ▁the ▁Sun . ▁The ▁" gra v it ational ▁drag " ▁of ▁this ▁resid ual ▁gas ▁would ▁have ▁eventually ▁lower ed ▁the ▁plan ets ' ▁energy , ▁sm o othing ▁out ▁their ▁or bits . ▁However , ▁such ▁gas , ▁if ▁it ▁existed , ▁would ▁have ▁prevent ed ▁the ▁terrest rial ▁plan ets ' ▁or bits ▁from ▁becoming ▁so ▁ecc ent ric ▁in ▁the ▁first ▁place . ▁Another ▁hypothesis ▁is ▁that ▁gravit ational ▁drag ▁occurred ▁not ▁between ▁the ▁plan ets ▁and ▁resid ual ▁gas ▁but ▁between ▁the ▁plan ets ▁and ▁the ▁remaining ▁small ▁bodies . ▁As ▁the ▁large ▁bodies ▁moved ▁through ▁the ▁crowd ▁of ▁smaller ▁objects , ▁the ▁smaller ▁objects , ▁attract ed ▁by ▁the ▁larger ▁plan ets ' ▁gravity , ▁formed ▁a ▁region ▁of ▁higher ▁density , ▁a ▁" gra v it ational ▁w ake ", ▁in ▁the ▁larger ▁objects ' ▁path . ▁As ▁they ▁did ▁so , ▁the ▁increased ▁gravity ▁of ▁the ▁w ake ▁slow ed ▁the ▁larger ▁objects ▁down ▁into ▁more ▁regular ▁or bits . ▁ ▁Ast ero id ▁bel t ▁The ▁outer ▁edge ▁of ▁the ▁terrest rial ▁region , ▁between ▁ 2 ▁and ▁ 4   AU ▁from ▁the ▁Sun , ▁is ▁called ▁the ▁astero id ▁bel t . ▁The ▁astero id ▁bel t ▁initially ▁contained ▁more ▁than ▁enough ▁matter ▁to ▁form ▁ 2 – 3 ▁Earth - like ▁plan ets , ▁and , ▁indeed , ▁a ▁large ▁number ▁of ▁plan