Radially homothetic spacetime is of Petrov-type D
  It is well-known \cite{mtbh} that {\em all} black hole solutions of General Relativity are of Petrov-type D. It may thus be expected that the spacetime of {\em physically realizable} spherical gravitational collapse is also of Petrov-type D. We show that a radially homothetic spacetime, {\em ie}, a spherically symmetric spacetime with hyper-surface orthogonal, radial, homothetic Killing vector, is of Petrov-type D. As has been argued in \cite{prl1}, it is a spacetime of {\em physically realizable} spherical collapse. 
Sanjay M Wagh and Keshlan S Govinder