Editing Neutron star (section)

===Neutron star binary mergers and nucleosynthesis===
{{Main|Neutron star merger}}

{{Multiple image
|perrow=2
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|image1=Neutron Stars Rip Each Other Apart to Form Black Hole (GSFC 20171208 Archive e001098).jpg
|image2=Neutron Stars Rip Each Other Apart to Form Black Hole (GSFC 20171208 Archive e001099).jpg
|image3=Neutron Stars Rip Each Other Apart to Form Black Hole (GSFC 20171208 Archive e001100).jpg
|image4=Neutron Stars Rip Each Other Apart to Form Black Hole (GSFC 20171208 Archive e001101).jpg
|footer=Four snapshots from a computer simulation of a neutron star merger. Clockwise, from top left:
#The two neutron stars make initial contact
#Immense tidal forces begin to disrupt the outer layers of the neutron stars
#The neutron stars are completely tidally disrupted
#A black hole forms, surrounded by an accretion disc
}}

The distance between two neutron stars in a close binary system is observed to shrink as [[gravitational waves]] are emitted.<ref>{{cite journal |last1=Taylor |first1=J. H. |last2=Weisberg |first2=J. M. |title=A new test of general relativity – Gravitational radiation and the binary pulsar PSR 1913+16 |journal=The Astrophysical Journal |date=15 February 1982 |volume=253 |page=908 |doi=10.1086/159690 |bibcode=1982ApJ...253..908T }}</ref> Ultimately, the neutron stars will come into contact and coalesce. The coalescence of binary neutron stars is one of the leading models for the origin of [[Gamma-ray burst#Short gamma-ray bursts|short gamma-ray bursts]]. Strong evidence for this model came from the observation of a [[kilonova]] associated with the short-duration gamma-ray burst GRB 130603B,<ref>{{cite journal |last1=Tanvir |first1=N. |last2=Levan |first2=A. J. |last3=Fruchter |first3=A. S. |last4=Hjorth |first4=J. |last5=Hounsell |first5=R. A. |last6=Wiersema |first6=K. |last7=Tunnicliffe |first7=R. L. |title=A 'kilonova' associated with the short-duration gamma-ray burst GRB 130603B |journal=Nature |date=2013 |volume=500 |issue=7464 |pages=547–549 |doi=10.1038/nature12505 |bibcode=2013Natur.500..547T |pmid=23912055 |arxiv=1306.4971 |s2cid=205235329 }}</ref> and was finally confirmed by detection of gravitational wave [[GW170817]] and short [[GRB 170817A]] by [[LIGO]], [[Virgo interferometer|Virgo]], and 70 observatories covering the electromagnetic spectrum observing the event.<ref name="SM-20171016">{{cite news |last=Cho |first=Adrian |title=Merging neutron stars generate gravitational waves and a celestial light show |url=https://www.science.org/content/article/merging-neutron-stars-generate-gravitational-waves-and-celestial-light-show |date=16 October 2017 |work=[[Science (magazine)|Science]] |access-date=16 October 2017 |archive-date=18 October 2017 |archive-url=https://web.archive.org/web/20171018011625/http://www.sciencemag.org/news/2017/10/merging-neutron-stars-generate-gravitational-waves-and-celestial-light-show |url-status=live }}</ref><ref name="NYT-20171016">{{cite news |last=Overbye |first=Dennis |author-link=Dennis Overbye |title=LIGO Detects Fierce Collision of Neutron Stars for the First Time |url=https://www.nytimes.com/2017/10/16/science/ligo-neutron-stars-collision.html |date=16 October 2017 |work=[[The New York Times]] |access-date=16 October 2017 |archive-date=16 October 2017 |archive-url=https://web.archive.org/web/20171016143216/https://www.nytimes.com/2017/10/16/science/ligo-neutron-stars-collision.html |url-status=live }}</ref><ref name="NAT-20170825">{{cite journal |last=Casttelvecchi |first=Davide |title=Rumours swell over new kind of gravitational-wave sighting |journal=[[Nature (journal)|Nature News]] |date=2017 |doi=10.1038/nature.2017.22482 }}</ref><ref name="PhysRev">{{cite journal|last1=Abbott|first1=B. P.|collaboration=[[LIGO Scientific Collaboration]] & [[Virgo interferometer|Virgo Collaboration]]|title=GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral|journal=Physical Review Letters|date=16 October 2017|volume=119|issue=16|pages=161101|doi=10.1103/PhysRevLett.119.161101|pmid=29099225|arxiv=1710.05832|bibcode=2017PhRvL.119p1101A|s2cid=217163611}}</ref> The light emitted in the kilonova is believed to come from the radioactive decay of material ejected in the merger of the two neutron stars. The merger momentarily creates an environment of such extreme neutron flux that the [[r-process|''r''-process]] can occur; this—as opposed to [[supernova nucleosynthesis]]—may be responsible for the production of around half the isotopes in [[chemical element]]s beyond [[iron]].<ref>{{cite web |url=http://www.cnn.com/2013/07/20/opinion/urry-gold-stars/index.html |title=Gold comes from stars |first=Meg |last=Urry |author-link=Meg Urry |work=CNN|date=July 20, 2013 |access-date=July 20, 2013 |archive-date=July 22, 2017 |archive-url=https://web.archive.org/web/20170722200821/http://www.cnn.com/2013/07/20/opinion/urry-gold-stars/index.html |url-status=live }}</ref>