Has the merger of a neutron star and an anti-neutron star been modeled?

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Discussion Overview

The discussion revolves around the hypothetical scenario of a neutron star colliding with an anti-neutron star, exploring the potential outcomes of such an event, including annihilation, black hole formation, and the dynamics of particle interactions. The scope includes theoretical modeling and speculative reasoning regarding high-energy astrophysical phenomena.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants propose that a collision could lead to complete annihilation, formation of a black hole, or partial annihilation with energy pushing remaining material away.
  • Others argue that the interactions are complex, with annihilation potentially resulting in a variety of particles being generated, including pions, neutrinos, photons, and muons, rather than a simple conversion to energy.
  • A participant notes that both partial and complete annihilation could leave significant amounts of matter behind, complicating the outcomes.
  • Concerns are raised about the lack of certainty in the equations of state for neutron stars, which could affect modeling efforts.
  • One participant suggests that the existence of an anti-neutron star is highly unlikely, which may explain the lack of modeling efforts in this area.
  • Another participant reflects on the differences in outcomes between direct head-on collisions and grazing impacts, indicating that the dynamics would vary significantly based on the nature of the collision.

Areas of Agreement / Disagreement

Participants express differing views on the outcomes of the collision, with no consensus reached on the likelihood of specific scenarios or the existence of anti-neutron stars. The discussion remains unresolved regarding the modeling of such events.

Contextual Notes

There are limitations regarding the understanding of neutron star interiors and the equations of state, which are not well-defined and may impact the theoretical modeling of neutron star and anti-neutron star collisions.

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TL;DR
What would happen if a neutron star and an antineutron star collided
If a neutron star and an anti neutron star collided, would they 1) completely annihilate each other, 2) form a black hole, or 3) partially annihilate each other with the remaining stars being pushed away from each other by the energy created?
 
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None of those options are mutually exclusive. Often we think of annihilation as two particles interacting with each other and turning into photons (so-called 'pure energy', which is more like two particles turning into two other particles). The reality is much more complicated though, especially when you get into composite particles and high-mass particles.

Protons and neutrons (and their anti- particles) often generate a shower of pions, which themselves decay into neutrinos, photons, and muons. Beyond the possible interactions and decays of pairs or single particles, the environment in a neutron star-antineutron star annihilation would be so energetic that you'd likely generate all kinds of different particles. I'd expect a portion of the stellar material to be blasted into space along with some of this newly created matter.

So there's not really a difference between a partial and a complete annihilation, as both can leave large amounts of matter behind.

As for option 2, this can happen regardless of the annihilation process. At least some portion of the annihilation and explosion could occur inside of the event horizon formed by the merger of the two stars.
 
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I'd add that I don't know that I'd expect a unique answer. A direct head-on collision is likely quite a different thing from a grazing impact.

I'd also add that I doubt that anyone's modelled this because as far as I know the equations of state in the interior of neutron stars are not known with any real certainty, and they'd matter a lot here.
 
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Probably nobody has spent any effort doing this because it is highly unlikely that an anti-neutron star exists in our universe.
 
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Correct...I was thinking of "complete annihilation" as leaving behind only photons -- that was mistaken. Yes, Ibix, I could imagine a grazing impact -- at what? more than half the speed of light? -- producing something very different from a head on collision. Would be something to see. Thanks for the answers.
 

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