Extreme mass-ratio inspiral

To first approximation, one can treat an extreme mass-ratio inspiral as an extreme mass-ratio binary orbit whose characteristics slowly evolve due to the backreaction of gravitational wave emission. This first video, made by Peter Reinhardt long ago, shows an example of what such an orbit looks like:

In Newtonian gravity, the orbit would be a simple ellipse confined to a particular plane. General relativistic gravity causes both the plane and the ellipse to precess, with the precession at periapsis so strong that the orbital “whirls” deep in the strong field before “zooming” back out to apoapsis.

By stitching together a sequence of such orbits, one produces the adiabatic approximation to an EMRI. The following video, made long ago by Steve Drasco shows an example. Steve’s video shows both the motion of the smaller body in the strong field of the black hole, as well as a sonification of the gravitational waveform that it produces.

The system shown here is of a 270 solar mass body spiralling into a 3 million solar mass black hole (with the time scales all compressed so that the signal is in the human audio band, and lasts a reasonable amount of time). The orbit is initially highly eccentric (e = 0.7 at t = 0), and is inclined 60° to the equatorial plane of the black hole. The black hole is spinning at 90% of the Kerr maximum.