# Neutron stars - Where are the protons?

**URL:** <https://boards.straightdope.com/t/neutron-stars-where-are-the-protons/135094>\
**Category:** Factual Questions\
**Created:** [November 3, 2002, 9:15am UTC](https://boards.straightdope.com/t/neutron-stars-where-are-the-protons/135094 "2002-11-03T09:15:13Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![starman](https://avatars.discourse-cdn.com/v4/letter/s/8c91f0/32.png) [@starman](https://boards.straightdope.com/u/starman)\
**Post date:** [November 3, 2002, 9:15am UTC](https://boards.straightdope.com/t/neutron-stars-where-are-the-protons/135094/1 "2002-11-03T09:15:13Z")

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When a star goes supernova, a neutron star may be produced. A neutron star is pretty much composed of a soup of neutrons and quarks, with a metal crust. the original star is mostly composed of protons, in the form of Hydrogen. So where do the protons (and electrons) go?  
My first guess would be that the protons and electrons somehow end up in the metal crust. Or perhaps the star is ‘melted’ completely down to quarks, and then rearranged into neutrons as it cools.  
Any thoughts?  
-Oli

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**Author:** ![Urban\_Ranger](https://avatars.discourse-cdn.com/v4/letter/u/e9c0ed/32.png) [@Urban\_Ranger](https://boards.straightdope.com/u/Urban_Ranger)\
**Post date:** [November 3, 2002, 10:57am UTC](https://boards.straightdope.com/t/neutron-stars-where-are-the-protons/135094/2 "2002-11-03T10:57:40Z")

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Protons and electrons are crushed together to form neutrons.

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**Author:** ![Illuvatar](https://avatars.discourse-cdn.com/v4/letter/i/b38774/32.png) [@Illuvatar](https://boards.straightdope.com/u/Illuvatar)\
**Post date:** [November 3, 2002, 11:34am UTC](https://boards.straightdope.com/t/neutron-stars-where-are-the-protons/135094/3 "2002-11-03T11:34:30Z")

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Just wondering, can the neutrons in a neutron star decay back into protons and electrons or does the immense gravity hold them together, or once they decay they immediately reform into an neutron? (my bets on the gravity holding them)

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**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\
**Post date:** [November 3, 2002, 3:26pm UTC](https://boards.straightdope.com/t/neutron-stars-where-are-the-protons/135094/4 "2002-11-03T15:26:20Z")

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Sorry, but how can “Starman” not know the answer to this?

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**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\
**Post date:** [November 3, 2002, 7:10pm UTC](https://boards.straightdope.com/t/neutron-stars-where-are-the-protons/135094/5 "2002-11-03T19:10:52Z")

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For that matter, how can **Illuvatar** not know? 😉

Ordinarily, neutrons are unstable, but under the intense pressures found in a neutron star, they are stable. And not all of the protons combine, either: I’ve seen estimates that as much as 10% of the mass of a neutron star may be protons. It’s just that there aren’t any other substances consisting of that many neutrons, so the neutrons are more remarkable (and besides, mostly-neutron-but-some-proton star just doesn’t have the same ring to it).