Editing Neutron star (section)

==Formation==
[[File:Neutronstarsimple.png|thumb|Simplified representation of the formation of neutron stars]]
Any [[main sequence|main-sequence]] star with an initial mass of greater than {{Solar mass|8|link=y}} (eight times the mass of the [[Sun]]) has the potential to become a neutron star. As the star evolves away from the main sequence, [[stellar nucleosynthesis]] produces an iron-rich core. When all nuclear fuel in the core has been exhausted, the core must be supported by degeneracy pressure alone. Further deposits of mass from shell burning cause the core to exceed the [[Chandrasekhar limit]]. Electron-degeneracy pressure is overcome, and the core collapses further, causing temperatures to rise to over {{val|5|e=9|u=K}} (5 billion K). At these temperatures, [[photodisintegration]] (the breakdown of iron nuclei into [[alpha particle]]s due to high-energy gamma rays) occurs. As the temperature of the core continues to rise, electrons and protons combine to form neutrons via [[electron capture]], releasing a flood of [[neutrino]]s. When densities reach a nuclear density of {{val|4|e=17|u=kg/m3}}, a combination of [[strong force]] repulsion and neutron degeneracy pressure halts the contraction.<ref>{{cite journal |first=I. |last=Bombaci |date=1996 |title=The Maximum Mass of a Neutron Star |journal=[[Astronomy and Astrophysics]] |volume=305 | pages=871–877 |bibcode=1996A&A...305..871B}}</ref> The contracting outer envelope of the star is halted and rapidly flung outwards by a flux of neutrinos produced in the creation of the neutrons, resulting in a [[supernova]] and leaving behind a neutron star. However, if the remnant has a mass greater than about {{Solar mass|3}}, it instead becomes a black hole.<ref>{{cite book |title=The Birth of Stars and Planets |edition=illustrated |first1=John |last1=Bally |first2=Bo |last2=Reipurth |publisher=Cambridge University Press |year=2006 |isbn=978-0-521-80105-8 |page=207 |url=https://books.google.com/books?id=Pwy9OtT8u6QC&pg=PA207 |access-date=2016-06-30 |archive-date=2017-01-31 |archive-url=https://web.archive.org/web/20170131193108/https://books.google.com/books?id=Pwy9OtT8u6QC&pg=PA207 |url-status=live }}</ref>

As the core of a massive star is compressed during a [[Type II supernova]] or a [[Type Ib and Ic supernovae|Type Ib or Type Ic]] supernova, and collapses into a neutron star, it retains most of its [[angular momentum]]. Because it has only a tiny fraction of its parent's radius (sharply reducing its [[moment of inertia]]), a neutron star is formed with very high rotation speed and then, over a very long period, it slows. Neutron stars are known that have rotation periods from about 1.4&nbsp;ms to 30&nbsp;s. The neutron star's density also gives it very high [[surface gravity]], with typical values ranging from {{val|e=12}} to {{val|e=13|u=m/s2}} (more than {{val|e=11}} times that of [[Earth]]).<ref name="Haensel">{{cite book |title=Neutron Stars |first1=Paweł |last1=Haensel |first2=Alexander Y. |last2=Potekhin |first3=Dmitry G. |last3=Yakovlev |isbn=978-0-387-33543-8 |publisher=Springer |date=2007 }}</ref> One measure of such immense gravity is the fact that neutron stars have an [[escape velocity]] of over half the [[speed of light]].<ref name="ChandraBlog 2013">{{cite web | title=The Remarkable Properties of Neutron Stars - Fresh Chandra News | website=ChandraBlog | date=2013-03-28 | url=https://chandra.harvard.edu/blog/node/432 | access-date=2022-05-16}}</ref> The neutron star's gravity accelerates infalling matter to tremendous speed, and [[tidal force]]s near the surface can cause [[spaghettification]].<ref name="ChandraBlog 2013"/>