Lifespan of Neutrons Adhering Together

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Discussion Overview

The discussion centers around the lifespan of neutrons, particularly in the context of neutrons adhering together, such as in neutron stars. Participants explore the implications of neutron interactions, stability, and the conditions that affect neutron decay, touching on theoretical and conceptual aspects of nuclear physics and astrophysics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant states that the lifespan of a single free neutron is about 15 minutes and questions whether this lifespan changes when neutrons adhere together.
  • Another participant argues that neutrons do not adhere together without protons, leading to the formation of atomic nuclei, each with its own stability.
  • A participant raises the question of how neutron stars can exist if neutrons do not adhere together.
  • It is suggested that neutron stars contain so many neutrons that they are held together by gravity.
  • Another participant questions how the lifespan of neutrons in a neutron star can exceed that of free neutrons.
  • One participant mentions degeneracy pressure, which prevents neutrons in a neutron star from collapsing indefinitely, referencing the Pauli exclusion principle and the energy states of protons and electrons.
  • There is a query about whether neutron stars are composed solely of neutrons or if there are also protons and electrons present, with a suggestion that the core contains a small percentage of these particles.
  • Another participant discusses Cooper pairing among neutrons and protons, relating it to superconductivity and superfluidity in neutron stars.
  • It is noted that neutrons in neutron stars do not decay due to their equilibrium with surrounding protons and electrons, similar to stable nuclei.

Areas of Agreement / Disagreement

Participants express various viewpoints regarding the interactions of neutrons, protons, and the conditions in neutron stars. There is no consensus on the specifics of neutron adherence, the implications for neutron lifespan, or the composition of neutron stars, indicating multiple competing views remain.

Contextual Notes

Participants reference complex concepts such as degeneracy pressure, Cooper pairing, and the Pauli exclusion principle without fully resolving the underlying mathematical or theoretical details. The discussion reflects a range of assumptions and interpretations regarding neutron behavior in different contexts.

jayaramas
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life of a single free neutron is nearly 15 min. what is the life if 2 are more neutrons adhering together? will it increase or same?
 
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Two or more neutrons don't adhere together unless you add some protons. If you add protons, you get atomic nuclei, and each nucleus has its own stability, which you can look up.
 
if neutrons are not adhering, how can there be a neutron star?
 
A neutron star has so many neutrons they are held together by gravity!
 
so, how is the life of neutron star more than a free neutron?
 
Well, I don't understand the maths, but the neutrons in a neutron star are prevented from collapsing indefinitely by what is called degeneracy pressure. This results from the Pauli exclusion principle - neutrons are fermions so no two can exist in the same state. The same condition applies to the protons and electrons they would have to decay into, and it must turn out that those states would have higher energy.

Actually, thinking about this now prompts a question in my mind: are neutron stars composed solely of neutrons, or are there still a limited number of proton and electron states available, with the numbers in each state determined by the respective energy levels?
 
AdrianTheRock said:
Well, I don't understand the maths, but the neutrons in a neutron star are prevented from collapsing indefinitely by what is called degeneracy pressure. This results from the Pauli exclusion principle - neutrons are fermions so no two can exist in the same state. The same condition applies to the protons and electrons they would have to decay into, and it must turn out that those states would have higher energy.

Actually, thinking about this now prompts a question in my mind: are neutron stars composed solely of neutrons, or are there still a limited number of proton and electron states available, with the numbers in each state determined by the respective energy levels?

In the core of a neutron star there are a few percent electrons and protons. This is why the core is superconducting. I imagine that the percentage decreases towards the center of the star.

According to the experts the neutrons are a superfluid, the protons are a superfluid, the electrons are an ordinary fluid. How they can be a superfluid I don't know.
 
The neutrons will do Cooper pairing with each other, and likewise with the protons. http://physicsworld.com/cws/article/news/45296

Cooper pairing is what's behind metal superconductivity and He-3 superfluidity.Neutron stars' neutrons don't decay because they are in equilibrium with the surrounding protons and electrons, just like neutrons in stable nuclei.

Neutron stars' protons are balanced out by their electrons, and that affects their composition. In a neutron-star interior, if protons were about as abundant as neutrons, the electrons would be squeezed together enough to bump their Fermi energies up to something not much less than proton and neutron rest masses. This tips the balance in favor of neutrons, and a neutron star's interior is thus mostly neutrons.

A nontechnical intro to NS's in general: Neutron stars
 

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