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The Null Geodesics of the Kerr Exterior
Samuel E. Gralla, Alexandru Lupsasca
The null geodesic equation in the Kerr spacetime can be expressed as a set of integral equations involving certain potentials. We classify the roots of these potentials and express…
Lensing by Kerr Black Holes
Samuel E. Gralla, Alexandru Lupsasca
Interpreting horizon-scale observations of astrophysical black holes demands a general understanding of null geodesics in the Kerr spacetime. These may be divided into two classes:…
Universal Interferometric Signatures of a Black Hole's Photon Ring
Michael D. Johnson, Alexandru Lupsasca, Andrew Strominger +14
The Event Horizon Telescope image of the supermassive black hole in the galaxy M87 is dominated by a bright, unresolved ring. General relativity predicts that embedded within this…
Particle motion near high-spin black holes
Daniel Kapec, Alexandru Lupsasca
General relativity predicts that the Kerr black hole develops qualitatively new and surprising features in the limit of maximal spin. Most strikingly, the region of spacetime near…