Black holes can bring dead white dwarf stars back to life shortly • The register

Black holes can bring dead stars back to life – even if only for a few seconds, according to a new study.

When stars stagger close to the imminent cavities, they can cause kickstart tidal disruption events (TDEs). Stars are drawn to the black hole by the strong gravitational field and eventually torn apart by the extreme tidal forces.

A group of physicists studied and modeled the interaction using computational simulations based on equations from the general theory of relativity. They discovered that during the violent process shining stars are destroyed, while dim white dwarfs left over from the core of the dead stars are generated. The strong tidal forces can compress the white dwarfs and activate thermonuclear reactions for a few seconds.


Images from computer simulations of a white dwarf that was just disturbed by a local black hole of 1000 solar masses. Image credit: Anninos et al.

It is a "probable outcome" if the white dwarf is huge enough and if the tidal compression is strong enough, according to the article on arXiv. The compressive strength depends on the mass of the black hole, which must lie in the intermediate mass range of approximately 100 to 100,000 times the mass of the sun.


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If a black hole is too small, gravity effects are minimal. However, if it is too big, it is more likely that the white dwarf is flooded by the black hole before the tidal forces can take over. Either way, the compression forces are not sufficient to start the thermonuclear melting process and the white dwarf remains dead.

"It's important to know how many black holes exist, because this will help answer the question where the super-heavy black holes come from," says Chris Fragile, co-author of the study and professor of physics and astronomy at the College of Charleston, South Carolina. "Finding an intermediate mass of black holes through events with tidal disruption would be a huge step forward."

The paper has been accepted and is expected to appear in The Astrophysical Journal. ®

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