  We suggest that the redshift of photons traveling from past to future null
infinity through a collapsing object could provide an observational signature
capable of differentiating between the formation of a globally naked
singularity and the formation of an event horizon. Supporting evidence for this
idea is drawn from the analysis of photons with zero angular momentum through
the center of a collapsing spherical dust cloud. We show that the frequency
shift as a function of proper time with respect to stationary observers has
distinct features depending on whether the object collapses to a black hole or
a naked singularity.
