After Neutron Star Death-Match, a Black Hole is Born

What happens when two neutron stars collide? Using a sophisticated computer simulation, NASA scientists have visualized this violent scenario in awesome degenerate-matter-crushing detail.

Neutron stars are the result of supernovae spawned by stars 8-30 times the mass of our sun. Occasionally, however, two neutron stars may meet, becoming entangled in a deep gravitational embrace. Should this scenario play out, one of the most powerful known explosions in the Universe may be sparked — a fast gamma-ray burst (GRB).

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But before two neutron stars collide, what happens to their structures? What kind of insanely powerful tidal forces are at play?

In a simulation released today (May 13) by NASA Goddard Space Flight Center scientists, two neutron stars are placed a mere 11 miles apart. Keep in mind that although both neutron stars are 1.5 and 1.7 time the mass of our sun, all of that matter is packed into a tiny sphere only 12 miles wide. As a result, their densities and gravitational fields are immense — a teaspoonful of neutron star material would weigh as much as Mount Everest. The crushing gravitational forces ensure that atomic structures cannot be sustained, collapsing the material into a neutron degenerate state — only the structure of the neutrons themselves prevent the neutron star’s gravity from collapsing it into a point, forming a black hole.

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Should more mass be added to the neutron star, a mass threshold may be reached when the gravitational forces overwhelm even the neutron degenerate pressure, causing it to collapse.

As the simulation unfolds, the neutron stars’ savage tidal forces rip each other to shreds, cracking open their thin crusts and shedding huge quantities of material into space. As they are so close to one another, the two neutron stars rapidly spin, merging in a fraction of a second. The progression of this simulated neutron star merger produces a ring doughnut-shaped material that forms about the genesis of the new-born black hole in its center.

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Simulating these violent events are important for our understanding of not only how some black holes are created, but it can develop the science behind GRBs. As an extension, the mysterious source of the heaviest elements in the Universe may be found in these events where the rapid cohesion of neutron stars — and the resulting explosions — could forge rapid-neutron capture (or ‘r-process‘) elements.

The majority of r-process elements — heavier than iron — found in the Universe are thought to be generated inside core-collapse supernovae. However, there’s a growing body of evidence that suggests merging neutron stars may be a fertile environment for the largest atomic nuclei to form.

So neutron star mergers are not only a fascinating field of astrophysical curiosity, they may also be the driving production mechanism responsible for the heaviest elements and complex chemistry throughout the Cosmos.

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