Editing Supernova (section)

====<span class="anchor" id="Electron-capture supernovae"></span> Electron-capture supernovae ====
In 1980, a "third type" of supernova was predicted by [[Ken'ichi Nomoto]] of the [[University of Tokyo]], called an electron-capture supernova. It would arise when a star "in the transitional range (~8 to 10 solar masses) between white dwarf formation and iron core-collapse supernovae", and with a [[degenerate matter|degenerate]] O+Ne+Mg core,<ref name=HowellEtAl2021-01a/> imploded after its core ran out of nuclear fuel, causing gravity to compress the electrons in the star's core into their atomic nuclei,<ref name=KeckObsNews2021-06-28-01a/><ref name=RTE2021-06-28-01a/> leading to a supernova explosion and leaving behind a neutron star.<ref name="heger"/> In June 2021, a paper in the journal ''[[Nature Astronomy]]'' reported that the 2018 supernova [[SN 2018zd]] (in the galaxy [[NGC 2146]], about 31 million light-years from Earth) appeared to be the first observation of an electron-capture supernova.<ref name=HowellEtAl2021-01a>{{cite journal |author1=Hiramatsu D |author2=Howell D |author3=Van S |display-authors=etal |date=28 June 2021 |title=The electron-capture origin of supernova 2018zd |url=https://www.nature.com/articles/s41550-021-01384-2 |journal=Nat Astron |volume=5 |issue=9 |pages=903–910 |doi=10.1038/s41550-021-01384-2 |arxiv=2011.02176 |bibcode=2021NatAs...5..903H |s2cid=226246044 |access-date=1 July 2021 |archive-date=30 June 2021 |archive-url=https://web.archive.org/web/20210630023436/https://www.nature.com/articles/s41550-021-01384-2 |url-status=live }}</ref><ref name=KeckObsNews2021-06-28-01a>{{cite web |url=https://keckobservatory.org/electron-capture-supernova |title=New, Third Type Of Supernova Observed |date=28 June 2021 |website=[[W. M. Keck Observatory]] |access-date=1 July 2021 |archive-date=29 June 2021 |archive-url=https://web.archive.org/web/20210629155228/https://www.keckobservatory.org/electron-capture-supernova |url-status=live }}</ref><ref name=RTE2021-06-28-01a>{{cite news|url=https://www.rte.ie/news/newslens/2021/0628/1231824-supernova-crab-nebula/|title=Astronomers discover new type of supernova|publisher=[[RTE News]]|author=|agency=[[Press Association|PA]]|date=28 June 2021|access-date=1 July 2021|quote=In 1980, Ken'ichi Nomoto of the University of Tokyo predicted a third type called an electron capture supernova. ... In an electron capture supernova, as the core runs out of fuel, gravity forces electrons in the core into their atomic nuclei, causing the star to collapse in on itself.|archive-date=30 June 2021|archive-url=https://web.archive.org/web/20210630165238/https://www.rte.ie/news/newslens/2021/0628/1231824-supernova-crab-nebula/|url-status=live}}</ref> The 1054 supernova explosion that created the Crab Nebula in our galaxy had been thought to be the best candidate for an electron-capture supernova, and the 2021 paper makes it more likely that this was correct.<ref name=KeckObsNews2021-06-28-01a/><ref name=RTE2021-06-28-01a/>