Self-similar planar Newtonian collapse

In this work, two different classes of planar solutions for cold dust are analysed within the Newtonian framework. The first class contains planar collapsing solutions for a general set of self-similar initial conditions extending, in this way, Penston's original results. The second class consists of solutions obtained without prescribing any initial conditions. In both classes, the solutions exhibit shell-crossing outside the plane of symmetry. The range of validity for both classes of solutions is then presented.