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How to Explore the Photon Sphere & ISCO 3D Explorer
Open the Photon Sphere & ISCO 3D Explorer, drag the Kerr spin-parameter slider, and watch the black hole's four orbit rings and its ergosphere update live from the exact Kerr formulas.
- Open https://freetoolonline.com/space-3d/photon-sphere-isco-explorer.html and wait for the black sphere, the four color-coded rings, and the purple ergosphere to render.
- Drag the Kerr spin parameter slider (a* = 0 to 0.998) to change the black hole's spin.
- Click "Reset (a*=0)" to jump to the non-spinning Schwarzschild case, or "Thorne limit (a*=0.998)" to jump to the astrophysical spin ceiling.
- Watch the cyan/magenta photon-orbit rings and the green/orange ISCO rings pull in (prograde) or push out (retrograde) as spin changes.
- Watch the purple frame-dragging arrows near the ergosphere spin faster as spin increases.
- Read the facts panel for the exact computed radii, in both M (gravitational-radius) and Rs (Schwarzschild-radius) units.
Key published figures
| Figure | Value |
|---|---|
| Photon sphere, Schwarzschild (a*=0) | 1.5 Rs = 3M |
| ISCO, Schwarzschild (a*=0) | 3 Rs = 6M |
| Extremal-spin limits | photon orbit 1M-4M, ISCO 1M-9M |
| Thorne astrophysical spin ceiling | a* ~= 0.998 |
Next: the when guide or vs alternatives. Open the Photon Sphere & ISCO 3D Explorer.
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