Editing Supernova (section)

==External impact==
Supernovae events generate heavier elements that are scattered throughout the surrounding interstellar medium. The expanding shock wave from a supernova can trigger star formation. Galactic cosmic rays are generated by supernova explosions.

===Source of heavy elements===
{{Main|Stellar nucleosynthesis|Supernova nucleosynthesis}}
[[File:Nucleosynthesis periodic table.svg|thumb|upright=2|Periodic table showing the source of each element in the interstellar medium]]

Supernovae are a major source of elements in the interstellar medium from oxygen through to rubidium,<ref name=nucleosynthesis/><ref name="François">
{{Cite journal
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 |last4=Spite |first4=M.
 |last5=Spite |first5=F.
 |last6=Chiappini |first6=C.
 |date=2004
 |title=The evolution of the Milky Way from its earliest phases: Constraints on stellar nucleosynthesis
 |journal=[[Astronomy & Astrophysics]]
 |volume=421 |issue=2 |pages=613–621
 |arxiv=astro-ph/0401499
 |bibcode=2004A&A...421..613F
 |doi=10.1051/0004-6361:20034140
|s2cid=16257700
 }}</ref><ref name="Truran">
{{cite book
 |last=Truran |first=J. W.
 |year=1977
 |chapter=Supernova Nucleosynthesis
 |editor-last=Schramm |editor-first=D. N.
 |title=Supernovae
 |series=Astrophysics and Space Science Library
 |volume=66 |pages=145–158
 |publisher=[[Springer Science+Business Media|Springer]]
 |doi=10.1007/978-94-010-1229-4_14 |bibcode=1977ASSL...66..145T
 |isbn=978-94-010-1231-7
}}</ref> though the theoretical abundances of the elements produced or seen in the spectra varies significantly depending on the various supernova types.<ref name="Truran"/> Type Ia supernovae produce mainly silicon and iron-peak elements, metals such as nickel and iron.<ref name=nomoto2018>{{cite journal|doi=10.1007/s11214-018-0499-0|title=Single Degenerate Models for Type Ia Supernovae: Progenitor's Evolution and Nucleosynthesis Yields|journal=Space Science Reviews|volume=214|issue=4|year=2018|last1=Nomoto|first1=Ken'Ichi|last2=Leung|first2=Shing-Chi|pages=67|arxiv=1805.10811|bibcode=2018SSRv..214...67N|s2cid=118951927}}</ref><ref name=maeda>{{cite journal|doi=10.1088/0004-637X/712/1/624|title=Nucleosynthesis in Two-Dimensional Delayed Detonation Models of Type Ia Supernova Explosions|journal=The Astrophysical Journal|volume=712|pages=624–638|year=2010|last1=Maeda|first1=K.|last2=Röpke|first2=F.K.|last3=Fink|first3=M.|last4=Hillebrandt|first4=W.|last5=Travaglio|first5=C.|last6=Thielemann|first6=F.-K.|issue=1|arxiv=1002.2153|bibcode=2010ApJ...712..624M|s2cid=119290875}}</ref> Core collapse supernovae eject much smaller quantities of the iron-peak elements than type Ia supernovae, but larger masses of light [[alpha element]]s such as oxygen and neon, and elements heavier than zinc. The latter is especially true with electron capture supernovae.<ref>{{Cite journal|doi = 10.1088/2041-8205/726/2/L15|title = Electron-Capture Supernovae as the Origin of Elements Beyond Iron|year = 2011|last1 = Wanajo|first1 = Shinya|last2 = Janka|first2 = Hans-Thomas|last3 = Müller|first3 = Bernhard|journal = The Astrophysical Journal|volume = 726|issue = 2|pages = L15|arxiv = 1009.1000|bibcode = 2011ApJ...726L..15W|s2cid = 119221889}}</ref> The bulk of the material ejected by type II supernovae is hydrogen and helium.<ref name=eichler>{{cite journal|doi=10.1088/1361-6471/aa8891|title=Nucleosynthesis in 2D core-collapse supernovae of 11.2 and 17.0 M⊙ progenitors: Implications for Mo and Ru production|journal=Journal of Physics G: Nuclear and Particle Physics|volume=45|pages=014001|year=2018|last1=Eichler|first1=M.|last2=Nakamura|first2=K.|last3=Takiwaki|first3=T.|last4=Kuroda|first4=T.|last5=Kotake|first5=K.|last6=Hempel|first6=M.|last7=Cabezón|first7=R.|last8=Liebendörfer|first8=M.|last9=Thielemann|first9=F-K|issue=1|arxiv=1708.08393|bibcode=2018JPhG...45a4001E|s2cid=118936429}}</ref> The heavy elements are produced by: nuclear fusion for nuclei up to <sup>34</sup>S; silicon photodisintegration rearrangement and quasiequilibrium during silicon burning for nuclei between <sup>36</sup>Ar and <sup>56</sup>Ni; and rapid capture of neutrons ([[r-process]]) during the supernova's collapse for elements heavier than iron. <!--Nucleosynthesis during silicon burning yields nuclei roughly 1,000 to 100,000 times more abundant than the r-process isotopes heavier than iron.<ref>
{{Cite journal
 |last=Woosley |first=S. E.
 |last2=Arnett |first2=W. D.
 |last3=Clayton |first3=D. D.
 |date=1973
 |title=The Explosive Burning of Oxygen and Silicon
 |journal=[[Astrophysical Journal Supplement]]
 |volume=26 |pages=231–312
 |bibcode=1973ApJS...26..231W
 |doi=10.1086/190282
}}</ref>--> The r-process produces highly unstable nuclei that are rich in [[neutron]]s and that rapidly beta decay into more stable forms. In supernovae, r-process reactions are responsible for about half of all the isotopes of elements beyond iron,<ref>
{{Cite journal
 |last1=Qian |first1=Y.-Z.
 |last2=Vogel |first2=P.
 |last3=Wasserburg |first3=G. J.
 |date=1998
 |title=Diverse Supernova Sources for the r-Process
 |journal=[[Astrophysical Journal]]
 |volume=494 |issue=1 |pages=285–296
 |bibcode=1998ApJ...494..285Q
 |doi=10.1086/305198
|arxiv=astro-ph/9706120|s2cid=15967473
 }}</ref> although [[neutron star merger]]s may be the main astrophysical source for many of these elements.<ref name=nucleosynthesis>{{cite journal|doi=10.1126/science.aau9540|pmid=30705182|title=Populating the periodic table: Nucleosynthesis of the elements|journal=Science|volume=363|issue=6426|pages=474–478|year=2019|last1=Johnson|first1=Jennifer A.|bibcode=2019Sci...363..474J|s2cid=59565697|doi-access=free}}</ref><ref name=siegel>{{cite journal |doi=10.1038/s41586-019-1136-0 |pmid=31068724 |title=Collapsars as a major source of r-process elements |journal=Nature |volume=569 |issue=7755 |pages=241–244 |year=2019 |last1=Siegel |first1=Daniel M. |last2=Barnes |first2=Jennifer |last3=Metzger |first3=Brian D. |arxiv=1810.00098 |bibcode=2019Natur.569..241S |s2cid=73612090 }}</ref>

In the modern universe, old [[asymptotic giant branch]] (AGB) stars are the dominant source of dust from oxides, carbon and [[s-process]] elements.<ref name=nucleosynthesis/><ref>
{{cite journal
 |last1=Gonzalez |first1=G.
 |last2=Brownlee |first2=D.
 |last3=Ward |first3=P.
 |year=2001
 |title=The Galactic Habitable Zone: Galactic Chemical Evolution
 |journal=Icarus
 |volume=152 |issue=1 |pages=185
 |arxiv=astro-ph/0103165
 |bibcode=2001Icar..152..185G
 |doi=10.1006/icar.2001.6617
|s2cid=18179704
 }}</ref> However, in the early universe, before AGB stars formed, supernovae may have been the main source of dust.<ref name=dust>{{cite journal |bibcode=2019BAAS...51c.351R |arxiv=1904.08485 |last1=Rho |first1=Jeonghee |title=Astro2020 Science White Paper: Are Supernovae the Dust Producer in the Early Universe? |journal=Bulletin of the American Astronomical Society |volume=51 |issue=3 |pages=351 |last2=Milisavljevic |first2=Danny |last3=Sarangi |first3=Arkaprabha |last4=Margutti |first4=Raffaella |last5=Chornock |first5=Ryan |last6=Rest |first6=Armin |last7=Graham |first7=Melissa |last8=Craig Wheeler |first8=J. |last9=DePoy |first9=Darren |last10=Wang |first10=Lifan |last11=Marshall |first11=Jennifer |last12=Williams |first12=Grant |last13=Street |first13=Rachel |last14=Skidmore |first14=Warren |last15=Haojing |first15=Yan |last16=Bloom |first16=Joshua |last17=Starrfield|author17-link=Sumner Starrfield |first17=Sumner |last18=Lee |first18=Chien-Hsiu |last19=Cowperthwaite |first19=Philip S. |last20=Stringfellow |first20=Guy S. |last21=Coppejans |first21=Deanne |last22=Terreran |first22=Giacomo |last23=Sravan |first23=Niharika |last24=Geballe |first24=Thomas R. |last25=Evans |first25=Aneurin |last26=Marion |first26=Howie |year=2019 }}
</ref>

===Role in stellar evolution===
{{Main|Supernova remnant}}
Remnants of many supernovae consist of a compact object and a rapidly expanding shock wave of material. This cloud of material sweeps up surrounding [[interstellar medium]] during a free expansion phase, which can last for up to two centuries. The wave then gradually undergoes a period of [[adiabatic process|adiabatic expansion]], and will slowly cool and mix with the surrounding interstellar medium over a period of about 10,000 years.<ref>
{{cite journal
 |last1=Cox |first1=D. P.
 |year=1972
 |title=Cooling and Evolution of a Supernova Remnant
 |journal=Astrophysical Journal
 |volume=178 |pages=159
 |bibcode=1972ApJ...178..159C
 |doi=10.1086/151775
|doi-access=free
 }}</ref>

[[Image:STScl-2005-15.png|thumb|upright=1.2|Supernova remnant N 63A lies within a clumpy region of gas and dust in the [[Large Magellanic Cloud]].]]
The [[Big Bang]] produced hydrogen, [[helium]] and traces of [[lithium]], while all heavier elements are synthesised in stars, supernovae, and collisions between neutron stars (thus being indirectly due to supernovae). Supernovae tend to enrich the surrounding interstellar medium with elements other than hydrogen and helium, which usually astronomers refer to as "metals".<ref name="Johnson2019">{{Cite journal |last=Johnson |first=Jennifer A. |date=February 2019 |title=Populating the periodic table: Nucleosynthesis of the elements |journal=Science |language=en |volume=363 |issue=6426 |pages=474–478 |doi=10.1126/science.aau9540 |pmid=30705182 |bibcode=2019Sci...363..474J |s2cid=59565697 |issn=0036-8075|doi-access=free }}</ref> These ejected elements ultimately enrich the [[molecular cloud]]s that are the sites of star formation.<ref>
{{cite journal
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 |last3=Stanimirović |first3=S. | author3-link=Snežana Stanimirović
 |last4=Van Loon |first4=J. Th.
 |last5=Smith |first5=J. D. T.
 |year=2009
 |title=Measuring Dust Production in the Small Magellanic Cloud Core-Collapse Supernova Remnant 1E 0102.2–7219
 |journal=The Astrophysical Journal
 |volume=696 |issue=2 |pages=2138–2154
 |arxiv=0810.2803
 |bibcode=2009ApJ...696.2138S
 |doi=10.1088/0004-637X/696/2/2138
|s2cid=8703787
 }}</ref> Thus, each stellar generation has a slightly different composition, going from an almost pure mixture of hydrogen and helium to a more metal-rich composition. Supernovae are the dominant mechanism for distributing these heavier elements, which are formed in a star during its period of nuclear fusion. The different abundances of elements in the material that forms a star have important influences on the star's life,<ref name="Johnson2019"/><ref>{{Cite journal |last1=Salaris |first1=Maurizio |last2=Cassisi |first2=Santi |date=August 2017 |title=Chemical element transport in stellar evolution models |doi-access=free |journal=Royal Society Open Science |language=en |volume=4 |issue=8 |pages=170192 |doi=10.1098/rsos.170192 |pmid=28878972 |pmc=5579087 |bibcode=2017RSOS....470192S |arxiv=1707.07454 |issn=2054-5703}}</ref> and may influence the possibility of having [[planet]]s orbiting it: more [[giant planet]]s form around stars of higher metallicity.<ref>{{cite journal|last1=Fischer |first1=Debra A. |last2=Valenti |first2=Jeff |title=The planet-metallicity correlation |journal=The Astrophysical Journal |bibcode=2005ApJ...622.1102F |doi=10.1086/428383 |volume=622 |year=2005 |issue=2 |pages=1102–1117|s2cid=121872365 |doi-access=free }}</ref><ref>{{cite journal|doi=10.1146/annurev-astro-112420-020055 |bibcode=2021ARA&A..59..291Z |arxiv=2103.02127 |title=Exoplanet Statistics and Theoretical Implications |journal=Annual Review of Astronomy and Astrophysics |volume=59 |year=2021 |last1=Zhu |first1=Wei |last2=Dong |first2=Subo |pages=291–336|s2cid=232105177 }}</ref>

The kinetic energy of an expanding supernova remnant can trigger star formation by compressing nearby, dense molecular clouds in space.<ref>
{{cite journal
 |last1=Preibisch |first1=T. 
 |last2=Zinnecker |first2=H. 
 |year=2001
 |title=Triggered Star Formation in the Scorpius-Centaurus OB Association (Sco OB2) 
 |journal=From Darkness to Light: Origin and Evolution of Young Stellar Clusters 
 |volume=243 |pages=791 
 |arxiv=astro-ph/0008013
 |bibcode=2001ASPC..243..791P
}}</ref> The increase in turbulent pressure can also prevent star formation if the cloud is unable to lose the excess energy.<ref name="aaa128">
{{cite journal
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 |last2=Hillebrandt |first2=W.
 |year=1983
 |title=The interaction of supernova shockfronts and nearby interstellar clouds
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}}</ref>

Evidence from daughter products of short-lived [[radioactive isotope]]s shows that a nearby supernova helped determine the composition of the [[Solar System]] 4.5&nbsp;billion years ago, and may even have triggered the formation of this system.<ref>
{{cite journal
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 |last2=Truran |first2=J.W.
 |year=1977
 |title=The supernova trigger for formation of the solar system
 |journal=Icarus
 |volume=30 |issue=3 |pages=447
 |bibcode=1977Icar...30..447C
 |doi=10.1016/0019-1035(77)90101-4
}}</ref>

[[Fast radio burst]]s (FRBs) are intense, transient pulses of radio waves that typically last no more than milliseconds. Many explanations for these events have been proposed; [[magnetar]]s produced by core-collapse supernovae are leading candidates.<ref name="AJL-20200601">{{cite journal |author=Bhandan, Shivani |date=1 June 2020 |title=The Host Galaxies and Progenitors of Fast Radio Bursts Localised with the Australian Square Kilometre Array Pathfinder |journal=[[The Astrophysical Journal Letters]] |volume=895 |pages=L37 |arxiv=2005.13160 |bibcode=2020ApJ...895L..37B |doi=10.3847/2041-8213/ab672e |s2cid=218900539 |number=2 |doi-access=free }}</ref><ref>{{Cite journal |last=Zhang |first=Bing |date=2020-11-05 |title=The physical mechanisms of fast radio bursts |url=https://www.nature.com/articles/s41586-020-2828-1 |journal=Nature |language=en |volume=587 |issue=7832 |pages=45–53 |doi=10.1038/s41586-020-2828-1 |pmid=33149290 |arxiv=2011.03500 |bibcode=2020Natur.587...45Z |s2cid=226259246 |issn=0028-0836}}</ref><ref>{{Cite web |last=Chu |first=Jennifer |date=2022-07-13 |title=Astronomers detect a radio "heartbeat" billions of light-years from Earth |url=https://news.mit.edu/2022/astronomers-detect-radio-heartbeat-billions-light-years-earth-0713 |access-date=2023-03-19 |website=MIT News |publisher=[[Massachusetts Institute of Technology]] |language=en}}</ref><ref>{{Cite journal |last1=Petroff |first1=E. |last2=Hessels |first2=J. W. T. |last3=Lorimer |first3=D. R. |date=2022-03-29 |title=Fast radio bursts at the dawn of the 2020s |url=https://doi.org/10.1007/s00159-022-00139-w |journal=The Astronomy and Astrophysics Review |language=en |volume=30 |issue=1 |pages=2 |doi=10.1007/s00159-022-00139-w |arxiv=2107.10113 |bibcode=2022A&ARv..30....2P |s2cid=253690001 |issn=1432-0754}}</ref>

===Cosmic rays===
Supernova remnants are thought to accelerate a large fraction of galactic primary [[cosmic ray]]s, but direct evidence for cosmic ray production has only been found in a small number of remnants. Gamma rays from [[pion]]-decay have been detected from the supernova remnants [[IC 443]] and W44. These are produced when accelerated [[proton]]s from the remnant impact on interstellar material.<ref name="ackermann-2013">
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===Gravitational waves===
Supernovae are potentially strong galactic sources of [[gravitational wave]]s,<ref>
{{Cite journal
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 }}</ref> but none have so far been detected. The only gravitational wave events so far detected are from mergers of black holes and neutron stars, probable remnants of supernovae.<ref name=morozova>{{cite journal|bibcode=2018ApJ...861...10M|doi=10.3847/1538-4357/aac5f1|title=The Gravitational Wave Signal from Core-collapse Supernovae|journal=The Astrophysical Journal|volume=861|issue=1|pages=10|year=2018|last1=Morozova|first1=Viktoriya|last2=Radice|first2=David|last3=Burrows|first3=Adam|last4=Vartanyan|first4=David|arxiv=1801.01914|s2cid=118997362 |doi-access=free }}</ref> Like the neutrino emissions, the gravitational waves produced by a core-collapse supernova are expected to arrive without the delay that affects light. Consequently, they may provide information about the core-collapse process that is unavailable by other means. Most gravitational-wave signals predicted by supernova models are short in duration, lasting less than a second, and thus difficult to detect. Using the arrival of a neutrino signal may provide a trigger that can identify the time window in which to seek the gravitational wave, helping to distinguish the latter from background noise.<ref>{{Cite journal |last1=Al Kharusi |first1=S. |last2=BenZvi |first2=S. Y. |last3=Bobowski |first3=J. S. |last4=Bonivento |first4=W. |last5=Brdar |first5=V. |last6=Brunner |first6=T. |last7=Caden |first7=E. |last8=Clark |first8=M. |last9=Coleiro |first9=A. |last10=Colomer-Molla |first10=M. |last11=Crespo-Anadón |first11=J. I. |last12=Depoian |first12=A. |last13=Dornic |first13=D. |last14=Fischer |first14=V. |last15=Franco |first15=D. |display-authors=14 |date=2021-03-01 |title=SNEWS 2.0: a next-generation supernova early warning system for multi-messenger astronomy |url=https://iopscience.iop.org/article/10.1088/1367-2630/abde33 |journal=New Journal of Physics |volume=23 |issue=3 |pages=031201 |doi=10.1088/1367-2630/abde33 |arxiv=2011.00035 |bibcode=2021NJPh...23c1201A |s2cid=226227393 |issn=1367-2630}}</ref>

===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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{{Cite journal
 |last1=Fields |first1=B. D.
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|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
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}}</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>