Super-extremal Kerr (a = 0.55 > M): a naked singularity. With no horizon there is no shadow; where the black disc would be, you see light that passed arbitrarily close to the singularity, wound into a chaotic core.
Super-extremal Kerr (a = 0.55 > M): a naked singularity. With no horizon there is no shadow; where the black disc would be, you see light that passed arbitrarily close to the singularity, wound into a chaotic core.
Kerr black hole with a checkerboard accretion disk showing frame dragging and lensing
Hot (8000 K) blackbody disc at a = 0.499, distant view (background image: M25)
The same disc up close: the shadow dominates, the disc wraps over the top, and the approaching side is visibly blueshifted
Cool (4000 K) blackbody disc at a = 0.4995 (essentially extremal; exactly a = M is degenerate as the ISCO meets the photon orbit), distant view
The extremal-limit disc up close
Kerr black hole with a checkerboard disk and volumetric rendering of the surrounding medium
Kerr black hole visualization with background stars and volumetric disc (background image: NGC 6355)
8000 K (exposure 5): deep amber; the cool outskirts thin toward transparency, stars showing through.
12000 K (exposure 1): the previous main-image temperature; pale gold, fully luminous end to end.
20000 K (exposure 0.13): pale ivory with a blue-white core. At matched brightness the frame is only mildly hotter-looking than 12000 K, because the visible-band blackbody chromaticity converges toward blue-white above ~10000 K; most of what higher temperature buys here is radiance, not color.
6x zoom onto the shadow's limb (12000 K scene): successive lensed images of the disc wind around the photon ring, each order ~23x thinner than the last (surface brightness is conserved, so each stays at full luminance until it falls below pixel scale; the grainy fringe is every deeper order averaging inside single pixels).
The control: the identical crop with the disc removed. The smooth boundary is the critical curve (its long straight stretch is the near-extremal "D-shape" flattening of the prograde limb at a/M = 0.998), and the faint concentric striations hugging it are the photon ring itself with only starlight as its source. Every winding in the image above slots into this scaffolding; same geometry, hot gas instead of faint stars as the paint.
Animation of a spinning Kerr black hole with a rotating accretion disk
Animation of a Kerr black hole with background stars and a rotating accretion disk (background image: M25)
Dragged porthole (just outside the horizon, looking straight out): the Schwarzschild porthole again, but frame dragging squeezes the sky circle off-axis and the plunging inner disc glow floods in from the sides.
Photon-shell edge, hovering just above the disc surface: the winding wall of stacked disc and sky images, with the glowing surface curving away beneath the camera.
Grazing view, skimming just above the disc surface inside its annulus: the multiple-winding band, distorted relative to Schwarzschild because prograde and retrograde light circle at different radii around a spinning hole.
Rearview: the magnified outward sky and the disc band, the near-side gas brightened by Doppler beaming.
Inside the ergosphere, looking prograde (the direction spacetime itself rotates): the winding wall seen from a region where standing still relative to the stars is impossible.
From the rotation axis, facing the hole: the disc face-on behind a shadow that stays circular; pole-on, even near-extremal spin barely distorts the silhouette, in contrast to every equatorial view.
From inside the gap between the disc's inner edge and the horizon, looking back along the orbit: the wound images pile up against the rim of the shadow.
The same spot, looking straight out: the sky and outer disc compressed into an oval by the gravity of the hole behind the camera.
Visualization of a ray trajectory approaching the event horizon of a Kerr black hole
