Gravitational Lensing

A massive foreground object bends spacetime, deflecting light from a background source. Perfect alignment produces an Einstein ring. Drag to move the source.

Lens mass M 1.00 Source X offset 0.3 Source Y offset 0.1 Source size 0.15

Einstein radius θ_E: –
Magnification μ: –
Images: –

Einstein radius (lens equation): θ_E = √(4GM D_ls / c² D_l D_s). Perfect alignment → ring. Off-axis → 2 images (major/minor arc). Microlensing events: point source crossing Einstein radius — achromatic brightening.