Spherical Symmetry/Simultaneity of Supernova Explosions

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Discussion Overview

The discussion revolves around the timing and symmetry of supernova explosions, particularly in comparison to the precise timing required in nuclear detonations. Participants explore the constraints on simultaneity in supernova events, potential asymmetries, and the mechanisms behind these explosions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether the timing of a supernova explosion has tight constraints similar to those of nuclear weapons, and asks about the estimated intervals and occurrences of asymmetrical explosions.
  • Another participant suggests that the core of a supernova is essentially spherical, but notes that observations may be limited to one direction, making asymmetry difficult to detect.
  • It is proposed that asymmetry in supernovae is likely due to differential rotation and varying angular momentum, citing the Crab nebula as an example of a misshapen remnant.
  • Some participants assert that current models do not support symmetric supernovae, as no successful models exist that can explain both the explosion and the resultant remnant.
  • A participant mentions the lack of successful models for type II supernova explosion mechanisms, highlighting a specific model that requires an off-center explosion for a carbon detonation supernova.
  • Questions are raised about the detonation interval for supernovae, with one participant noting that the explosion mechanism differs from that of nuclear weapons, suggesting that the timing of outer layer infall may not be critical.
  • Another participant speculates on the possibility of a supernova explosion developing over a longer time span, questioning if there is an upper limit to this interval.
  • It is noted that the collapse of the stellar core occurs on a freefall timescale of seconds, with observations from Supernova 1987a indicating that the explosion can develop over several hours, particularly for more massive stars.

Areas of Agreement / Disagreement

Participants express differing views on the symmetry of supernova explosions, with some asserting that asymmetry is inherent while others discuss the potential for symmetric models. The discussion remains unresolved regarding the exact timing constraints and mechanisms involved in supernova explosions.

Contextual Notes

There are limitations in the current understanding of supernova mechanisms, particularly regarding type II supernovae, and the dependence on observational data may restrict conclusions about asymmetry and timing.

Islam Hassan
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If the timing of detonation of nuclear weapons’ numerous implosive lenses must to be kept to within a microsecond or so in order to avoid asymmetrical detonation, does the timing of a supernova explosion similarly have tight constraints on its simultaneity and hence the sphericity of its ultimate cataclysmic implosion/explosion?

What are these constraints estimated to be, and are they occasionally breached? Have we observed asymmetric —or slightly asymmetric— supernova explosions?IH
 
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Above should help. The core is essentially spherical, so there is no reason to expect anything else. However our observations are from one direction, so asymmetry may be hard to detect.
 
There's going to be asymmetry due to differential rotation - varying angular momentum with angle from the equator. Look at the Crab nebula - it's somewhat misshapen and oblong.
 
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As far as we know, supernovae are asymmetric. There is no models of symmetric supernovae that provide a) an explosion and b) a remnant. Since we see both, we know the symmetric models are wrong.
 
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To explain further - We still don't have successful models of type II supernova explosion mechanisms, so we don't know how they explode. Don Lamb at the University of Chicago was able to produce a successful model of a carbon detonation supernove - one produced by an accreting white dwarf star - but only if the explosion originated off-center.
 
If the numerous implosive lenses on a nuclear weapon typically have to detonate within less than a microsecond, do we have an estimate of the ‘detonation’ interval window for supernovae?IH
 
Islam Hassan said:
If the numerous implosive lenses on a nuclear weapon typically have to detonate within less than a microsecond, do we have an estimate of the ‘detonation’ interval window for supernovae?IH
The explosion mechanism for a supernova is not the same as for a nuclear weapon. The core of the massive star that forms the supernova turns into a neutron star that doesn't detonate, so the timing of the infall of the outer layers of the star is less critical for production of the explosion. Indeed, we're not sure if the outer layers of the star infall at all before the explosion occurs.
 
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Thanks for all your answers. Conceivably then, could a supernova explosion develop fully over a span of minutes or hours even? Would there theoretically be an upper limit on this time interval?IH
 
The collapse of the stellar core to becoming a neutron star occurs on a freefall timescale and takes only a matter of seconds! Observations of neutrinos coming from the core of Supernova 1987a came several hours before the light signal from the event was observed, so the explosion developed over the span of a few hours. Presumably the more massive the star, the longer the interval for the explosion to develop.
 
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