GRG Editor's Choice: Shadows and strong gravitational lensing – a brief review

© SpringerPedro V. P. Cunha & Carlos A. R. Herdeiro, Shadows and strong gravitational lensing: a brief review, Gen Relativ Gravit (2018) 50: 42.

Editor's Choice (Invited Review: State of the Field)

First Online: 20 March 2018

Part of the Topical Collection: "Testing the Kerr spacetime with gravitational-wave and electromagnetic observations"

"This brief review is well-written and timely provides useful information on shadows and relativistic lensing by black holes and ultra compact objects."


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.

The authors: 

Herdeiro-Cunha © Springer

Carlos A. R. Herdeiro is Principal Researcher at the Physics Department of Aveiro University, Portugal.

Pedro V. P. Cunha is pursuing his PhD studies at the University of Aveiro and the Centre for Astrophysics and Gravitation of the IST - University of Lisbon, Portugal.

GRG Editor's Choice:

In each volume of GRG, a few papers are marked as “Editor’s Choice”. The primary criteria is original, high quality research that is of wide interest within the community.