Black Hole Imager

Place planets, stars, cubes, rings or a whole lattice around a rotating black hole, choose where you are and how you move – hovering, orbiting, falling in or flying past at nearly the speed of light – and see the scene the way your eye would.

Every pixel is traced backwards along an exact light path (null geodesic) of the Kerr metric. Frame dragging, the flattened shadow of a fast-spinning hole, Einstein rings, multiple images and the photon ring all follow from the equations; the shadow edge can be checked against the analytic solution with one click.

Colours are computed from spectra: stars, the Novikov–Thorne accretion disk and glowing objects are black bodies, painted objects reflect white light. Gravitational redshift, the Doppler effect of moving sources, your own motion and relativistic beaming shift each spectrum before it is turned into the colour you would see. Moving objects and the rotating disk are shown where they were when their light left them.

Real-time preview while you move, progressive refinement when you stop, and high-resolution renders (up to 8K or 360° panoramas) as PNG. Analysis views show the frequency shift, the number of turns each ray made around the hole and the light travel time. Runs entirely in your browser (WebGL 2).