What is superfluidity in neutron stars explained with crayons?

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Discussion Overview

The discussion revolves around the concept of superfluidity in neutron stars, particularly its implications for cooling processes. Participants explore the relationship between superfluidity and the thermal behavior of neutron stars, with a focus on theoretical models and observable effects.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that superfluidity in neutron stars is not surprising given that nuclei exhibit superfluid properties, but questions the connection between superfluidity and cooling.
  • Another participant expresses uncertainty about the current understanding of neutron star cooling, indicating a lack of clarity in the field.
  • A detailed explanation is provided regarding the structure of neutron stars, mentioning that superfluidity arises from nucleons pairing in different states depending on density, specifically the 1S0 state near the surface and the 3P2 state deeper within.
  • The cooling process is discussed, highlighting that neutrons form a degenerate Fermi gas and that cooling primarily occurs through the Urca process, with superfluidity potentially introducing new cooling mechanisms via neutrino emissions from bound pair states.
  • A humorous interjection about crayons is made, suggesting a light-hearted approach to the complex topic.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the relationship between superfluidity and cooling in neutron stars, with some expressing clarity on certain aspects while others indicate confusion and uncertainty.

Contextual Notes

The discussion reflects limitations in understanding the observable effects of superfluidity on neutron star cooling, with participants acknowledging the complexity of the topic and the need for further observational confirmation.

bcrowell
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I thought others might be interested in this: http://arxiv.org/abs/1011.6142

As a nuclear physicist, I don't find it surprising to hear that neutron stars are superfluid. Nuclei are superfluid. I'm not clear on the relationship between superfluidity and cooling. Can anyone explain this using crayons?
 
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You are in good company - http://news.discovery.com/space/the-neutron-star-cooling-mystery.html . We are basically clueless.
 
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Crayons? Well, crayons are the carriers of the color force, and... no wait, let's start over.
The known structure of neutron stars is getting pretty complex, and superfluidity plays an important part. In a region near the surface, the density is below what's found in nuclei. Here, superfluidity results from nucleons (both n and p) pairing in the 1S0 state, much like they do in nuclei. Nearer the center, however, the density is so great that the repulsive core in the 1S0 state becomes important. The neutrons now prefer the 3P2 state, and this is the superfluidity that they're talking about. (There's still a few protons around.)
This has all been known for some time, and the issue is what observable effect it has on the cooling rate. The neutrons form a degenerate Fermi gas, making the available transitions few. Most of the cooling normally comes from the Urca process (beta decays, n to p and vice versa). Any neutrinos that are formed easily escape, carrying away their energy.
Once superfluidity occurs, the bound pair state becomes available, and transitions to and from this state can happen with emission of a neutrino-antineutrino pair. This is what causes the extra cooling. They're hoping that the observations continue to confirm this theoretical picture.
 


Bill_K said:
Crayons? Well, crayons are the carriers of the color force, and... no wait, let's start over.

all i have to say is... lol
 

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