Gravitational Lensing — Einstein Ring & Deflection

A massive lens deflects light by α̂ = 4GM/(c²b) per impact parameter b (GR factor of 2 over Newtonian). Perfect alignment source-lens-observer produces an Einstein ring of angular radius θ_E = √(4GM D_ls / c² D_l D_s).

Einstein radius θ_E = — arcsec | Magnification μ = — | Source offset β = — θ_E

Lens mass M: 1.0 (×10¹¹M☉) Source offset: 0.0 D_ls/D_s: 0.5