Gravitational collapse

Gravitational collapse to a rotating black hole

Collapse with excision: matter fields

This visualization of a computer simulation shows the gravitational collapse of a neutron star to a rotating black hole. Such a collapse is one of the strongest sources of electromagnetic and gravitational radiation. But only a millionth part of the system energy is emitted as gravitational waves, so the computations have to be very accurate, and the numerical problem is quite challenging. Furthermore, in order to make good predictions of possible gravitational wave signals, the simulation has to be carried out on a large spacial region, as the gravitational waves take their so-called asymptotic form - how we can detect them on earth - only far away from the source. With the numerical method used here it was possible for the first time to compute the gravitational radiation of such an event with an all three-dimensional simulation.

These images show the collapsing rotating neutron star, illustrated by its matter density (blue and magenta for different densities). The rotation is visualized by the velocity vectors (yellow arrows) in one plane of the star, showing that the matter is rotating even faster while collapsing. At least the apparent horizon (white) forms at the center. This is - at a given time step - the boundary between regions where outgoing light rays can still escape to infinity and where they are trapped in the black hole. As the region of space inside the horizon has no effect on the outer space, it has been excised in this simulation - this way one avoids the numerical problem of handling the singularity inside the black hole where the curvature of spacetime becomes infinite.

I. Hawke (University of Southampton), L. Baiotti (SISSA), L. Rezzolla (Max Planck Institute for Gravitational Physics, Institute for Theoretical Physics, Frankfurt, SISSA)

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