Editing Supernova (section)

===Effect on Earth===
{{Main|Near-Earth supernova}}
A near-Earth supernova is a supernova close enough to the Earth to have noticeable effects on its [[biosphere]]. Depending upon the type and energy of the supernova, it could be as far as 3,000 light-years away.
In 1996 it was theorised that traces of past supernovae might be detectable on Earth in the form of metal isotope signatures in [[rock strata]]. [[Iron#Isotopes|Iron-60]] enrichment was later reported in deep-sea rock of the [[Pacific Ocean]].<ref>
{{cite journal
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 |last3=Ellis |first3=J.
 |year=2005
 |title=Deep-Ocean Crusts as Telescopes: Using Live Radioisotopes to Probe Supernova Nucleosynthesis
 |journal=The Astrophysical Journal
 |volume=621 |issue=2 |pages=902–907
 |arxiv=astro-ph/0410525
 |bibcode=2005ApJ...621..902F
 |doi=10.1086/427797
|s2cid=17932224
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 |date=2004
 |title=<sup>60</sup>Fe Anomaly in a Deep-Sea Manganese Crust and Implications for a Nearby Supernova Source
 |journal=[[Physical Review Letters]]
 |volume=93
 |issue=17
 |pages=171103–171106
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{{Cite journal
 |last1=Fields |first1=B. D.
 |last2=Ellis |first2=J.
 |date=1999
 |title=On Deep-Ocean Fe-60 as a Fossil of a Near-Earth Supernova
 |journal=[[New Astronomy (journal)|New Astronomy]]
 |volume=4 |issue=6 |pages=419–430
 |arxiv=astro-ph/9811457
 |bibcode=1999NewA....4..419F
 |doi=10.1016/S1384-1076(99)00034-2
|s2cid=2786806
 }}</ref> In 2009, elevated levels of nitrate ions were found in Antarctic ice, which coincided with the 1006 and 1054 supernovae. Gamma rays from these supernovae could have boosted atmospheric levels of nitrogen oxides, which became trapped in the ice.<ref>
{{cite journal
 |year=2009
 |title=In Brief
 |journal=Scientific American
 |volume=300 |issue=5 |pages=28
 |bibcode=2009SciAm.300e..28.
 |doi=10.1038/scientificamerican0509-28a
}}</ref>

Historically, nearby supernovae may have influenced the [[biodiversity]] of life on the planet. Geological records suggest that nearby supernova events have led to an increase in cosmic rays, which in turn produced a cooler climate. A greater temperature difference between the poles and the equator created stronger winds, increased ocean mixing, and resulted in the transport of [[nutrients]] to shallow waters along the [[continental shelves]]. This led to greater biodiversity.<ref>{{cite news
 | title=Did Supernovae Help Push Life to Become More Diverse?
 | first=Carolyn Collins | last=Petersen
 | work=Universe Today | date=March 22, 2023
 | url=https://www.universetoday.com/160686/did-supernovae-help-push-life-to-become-more-diverse/
 | access-date=2023-03-23
}}</ref><ref>{{cite journal
 | title=A persistent influence of supernovae on biodiversity over the Phanerozoic
 | first=Henrik | last=Svensmark | author-link=Henrik Svensmark
 | journal=Ecology and Evolution
 | volume=13 | issue=3 | id=e9898 | date=March 16, 2023
 | pages=e9898 | publisher=Wiley Online Library | doi=10.1002/ece3.9898
| pmid=36937070 | pmc=10019915 | bibcode=2023EcoEv..13E9898S }}</ref>

Type Ia supernovae are thought to be potentially the most dangerous if they occur close enough to the Earth. Because these supernovae arise from dim, common white dwarf stars in binary systems, it is likely that a supernova that can affect the Earth will occur unpredictably and in a star system that is not well studied. The closest-known candidate is [[IK Pegasi]] (HR 8210), about 150 light-years away,<ref>
{{Cite journal
 |last=Gorelick |first=M.
 |date=2007
 |title=The Supernova Menace
 |journal=[[Sky & Telescope]]
 |volume=113 |issue=3 |page=26
 |bibcode=2007S&T...113c..26G
}}</ref><ref>
{{Cite journal |last1=Landsman |first1=W. |last2=Simon |first2=T. |last3=Bergeron |first3=P. |date=1999 |title=The hot white-dwarf companions of HR 1608, HR 8210, and HD 15638 |journal=[[Publications of the Astronomical Society of the Pacific]] |volume=105 |issue=690 |pages=841–847 |bibcode=1993PASP..105..841L |doi=10.1086/133242 |doi-access=free}}</ref> but observations suggest that it could be as long as 1.9&nbsp;billion years before the white dwarf can accrete the critical mass required to become a type Ia supernova.<ref>{{Cite journal |last=Beech |first=Martin |date=December 2011 |title=The past, present and future supernova threat to Earth's biosphere |url=http://link.springer.com/10.1007/s10509-011-0873-9 |journal=Astrophysics and Space Science |language=en |volume=336 |issue=2 |pages=287–302 |bibcode=2011Ap&SS.336..287B |doi=10.1007/s10509-011-0873-9 |issn=0004-640X |s2cid=119803426}}</ref> 

According to a 2003 estimate, a type II supernova would have to be closer than {{Convert|8|pc|lk=in|abbr=off}} to destroy half of the Earth's ozone layer, and there are no such candidates closer than about 500 light-years.<ref name="Gehrels">
{{Cite journal
 |last1=Gehrels |first1=N.
 |last2=Laird |first2=C. M.
 |last3=Jackman |first3=C. H.
 |last4=Cannizzo |first4=J. K.
 |last5=Mattson |first5=B. J.
 |last6=Chen |first6=W.
 |date=2003
 |title=Ozone Depletion from Nearby Supernovae
 |journal=[[Astrophysical Journal]]
 |volume=585|issue=2 |pages=1169–1176
 |arxiv=astro-ph/0211361
 |bibcode=2003ApJ...585.1169G
 |doi=10.1086/346127
|s2cid=15078077
 }}</ref>