  We attempt to address the question of whether standard tests of general
relativity can detect the presence of a black hole carrying a supertranslation
field. In this regard, we study the photon sphere of a dynamical black hole
carrying a supertranslation hair. We find that the dynamics of the photon
sphere is quite subtle and it may offer an opportunity to differentiate a
supertranslated black hole from its bald counterpart. This represents a first
step towards understanding the observational signatures of a supertranslated
dynamical black hole.
