Black Hole

This 3D black hole simulation shows gas orbiting outside the event horizon, the dark shadow about 2.6 times the horizon radius, and the brighter side of the disk that moves towards you. Sliders set the mass from 3 to 100 solar masses and the tilt of the disk, and a toggle controls the Doppler glare. Readouts give the horizon radius, innermost stable orbit, orbit period and speed. Teachers can use it to link mass to size and to explain why one side of a rotating disk looks brighter.

• Raise the Mass slider and watch the Horizon radius r_s readout grow in kilometers.
• Tilt the disk from 5 to 85 degrees and see how the bent ring of light changes shape.
• Switch Doppler glare off, then on, to see why the approaching side looks brighter.
• Read the Orbit speed at ISCO and compare it with the speed of light.
• Drag to orbit the camera and zoom in to compare the horizon, the shadow edge and the innermost stable orbit labels.

1. 1Describe what the event horizon of a black hole is and how its radius depends on mass.
2. 2Explain why a rotating disk looks brighter on the side moving towards the viewer.
3. 3Recognize that gravity bends light, producing a ring around a dark shadow.
4. 4Compare orbit speeds and sizes for black holes of different masses.

Questions teachers ask