Shadows and strong gravitational lensing: a brief review

  • Pedro V. P. CunhaEmail author
  • Carlos A. R. Herdeiro
Editor’s Choice (Invited Review: State of the Field)
Part of the following topical collections:
  1. Testing the Kerr spacetime with gravitational-wave and electromagnetic observations


For ultra compact objects, light rings and fundamental photon orbits (FPOs) play a pivotal role in the theoretical analysis of strong gravitational lensing effects, and of BH shadows in particular. In this short review, specific models are considered to illustrate how FPOs can be useful in order to understand some non-trivial gravitational lensing effects. This paper aims at briefly overviewing the theoretical foundations of these effects, touching also some of the related phenomenology, both in general relativity and alternative theories of gravity, hopefully providing some intuition and new insights for the underlying physics, which might be critical when testing the Kerr black hole hypothesis.


Strong gravitational lensing Black hole shadow 



We would like to thank E. Berti, J. Grover, E. Radu, H. Rúnarsson, A. Wittig for collaboration on some of the work reviewed in this paper. We would also like to thank all the participants in the Gravitational lensing and black hole shadows workshop that took place in Aveiro, Portugal, in November 2016, for many stimulating discussions on these topics. P.C. is supported by Grant No. PD/BD/114071/2015 under the FCT-IDPASC Portugal Ph.D. program. C.H. acknowledges funding from the FCT-IF programme. This work was partially supported by the H2020-MSCA-RISE-2015 Grant No. StronGrHEP-690904, the H2020-MSCA-RISE-2017 Grant No. FunFiCO-777740 and by the CIDMA Project UID/MAT/04106/2013 The authors would like to acknowledge networking support by the COST Action CA16104.


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© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Departamento de FísicaUniversidade de Aveiro and CIDMAAveiroPortugal
  2. 2.Centro de Astrofísica e Gravitação - CENTRA, Departamento de Física, Instituto Superior Técnico - ISTUniversidade de Lisboa - ULLisboaPortugal

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