This video clip compares the effects on emission lines of spinning and non-spinning black holes.
The video first shows the non-spinning black hole. The accretion disk rotates around the black hole. Note that there is a gap between the inner edge of the accretion disk and the black hole itself. The graph at the bottom shows the shape of the emission from the disk.
The video then shows a spinning black hole. Again the accretion disk rotates around the black hole. Note that disk comes closer to the black hole. The graph at the bottom shows the shape of the emission line.
The animation ends with a side-by-side comparison of the non-spinning and the spinning black holes. The emission from the spinning black hole is less intense than from the non-spinning black hole. It is also spread out over a wider energy range. The rotation of the black hole allows for gas in the disk to get closer. This gas is subjected to a stronger gravitational redshift and higher velocities. These two effects spread the the line over a larger energy range.
