Editing Supernova (section)

===Progenitor===
[[File:Artist's impression time-lapse of distant supernovae.webm|thumb|Occasional supernovae appear in this sped-up artist's impression of distant galaxies. Each exploding star briefly rivals the brightness of its host galaxy.]]
The supernova classification type is closely tied to the type of progenitor star at the time of the collapse. The occurrence of each type of supernova depends on the star's metallicity, since this affects the strength of the stellar wind and thereby the rate at which the star loses mass.<ref>{{Cite journal |last1=Ganss |first1=R |last2=Pledger |first2=J L |last3=Sansom |first3=A E |last4=James |first4=P A |last5=Puls |first5=J |last6=Habergham-Mawson |first6=S M |date=22 March 2022 |title=Metallicity estimation of core-collapse Supernova H ii regions in galaxies within 30 Mpc |doi-access=free|journal=Monthly Notices of the Royal Astronomical Society |language=en |volume=512 |issue=1 |pages=1541–1556 |doi=10.1093/mnras/stac625 |issn=0035-8711 |bibcode=2022MNRAS.512.1541G |arxiv=2203.03308 }}</ref>

Type Ia supernovae are produced from white dwarf stars in binary star systems and occur in all [[Galaxy morphological classification|galaxy types]].<ref>{{Cite journal |last1=Prochaska |first1=J. X. |last2=Bloom |first2=J. S. |last3=Chen |first3=H.-W. |last4=Foley |first4=R. J. |last5=Perley |first5=D. A. |last6=Ramirez-Ruiz |first6=E. |last7=Granot |first7=J. |last8=Lee |first8=W. H. |last9=Pooley |first9=D. |last10=Alatalo |first10=K. |last11=Hurley |first11=K. |last12=Cooper |first12=M. C. |last13=Dupree |first13=A. K. |last14=Gerke |first14=B. F. |last15=Hansen |first15=B. M. S. |date=10 May 2006 |title=The Galaxy Hosts and Large-Scale Environments of Short-Hard Gamma-Ray Bursts |doi-access=free |journal=The Astrophysical Journal |language=en |volume=642 |issue=2 |pages=989–994 |doi=10.1086/501160 |issn=0004-637X |bibcode=2006ApJ...642..989P |arxiv=astro-ph/0510022 }}</ref> Core collapse supernovae are only found in galaxies undergoing current or very recent star formation, since they result from short-lived massive stars. They are most commonly found in type Sc spirals, but also in the arms of other spiral galaxies and in [[irregular galaxy|irregular galaxies]], especially [[Starburst galaxy|starburst galaxies]].<ref>{{Cite journal |last1=Petrosian |first1=Artashes |last2=Navasardyan |first2=Hripsime |last3=Cappellaro |first3=Enrico |last4=McLean |first4=Brian |last5=Allen |first5=Ron |last6=Panagia |first6=Nino |last7=Leitherer |first7=Claus |last8=MacKenty |first8=John |last9=Turatto |first9=Massimo |date=March 2005 |title=Active and Star-forming Galaxies and Their Supernovae |doi-access=free |journal=The Astronomical Journal |language=en |volume=129 |issue=3 |pages=1369–1380 |doi=10.1086/427712 |bibcode=2005AJ....129.1369P |issn=0004-6256}}</ref><ref>{{Cite journal |last1=Shao |first1=X. |last2=Liang |first2=Y. C. |last3=Dennefeld |first3=M. |last4=Chen |first4=X. Y. |last5=Zhong |first5=G. H. |last6=Hammer |first6=F. |last7=Deng |first7=L. C. |last8=Flores |first8=H. |last9=Zhang |first9=B. |last10=Shi |first10=W. B. |last11=Zhou |first11=L. |date=25 July 2014 |title=Comparing the Host Galaxies of Type Ia, Type II, and Type Ibc Supernovae |doi-access=free |journal=The Astrophysical Journal |volume=791 |issue=1 |pages=57 |doi=10.1088/0004-637X/791/1/57 |bibcode=2014ApJ...791...57S |arxiv=1407.0483 |issn=0004-637X}}</ref><ref>{{Cite journal |last1=Taggart |first1=K |last2=Perley |first2=D A |date=5 April 2021 |title=Core-collapse, superluminous, and gamma-ray burst supernova host galaxy populations at low redshift: the importance of dwarf and starbursting galaxies |doi-access=free |journal=Monthly Notices of the Royal Astronomical Society |language=en |volume=503 |issue=3 |pages=3931–3952 |bibcode=2021MNRAS.503.3931T |arxiv=1911.09112 |doi=10.1093/mnras/stab174 |issn=0035-8711}}</ref>

Type Ib and Ic supernovae are hypothesised to have been produced by core collapse of massive stars that have lost their outer layer of hydrogen and helium, either via strong stellar winds or mass transfer to a companion.<ref name="arxiv"/> They normally occur in regions of new star formation, and are extremely rare in [[Elliptical galaxy|elliptical galaxies]].<ref name="Perets-2010"/> The progenitors of type IIn supernovae also have high rates of mass loss in the period just prior to their explosions.<ref>{{Cite journal |last1=Moriya |first1=Takashi J. |last2=Maeda |first2=Keiichi |last3=Taddia |first3=Francesco |last4=Sollerman |first4=Jesper |last5=Blinnikov |first5=Sergei I. |last6=Sorokina |first6=Elena I. |date=11 April 2014 |title=Mass-loss histories of Type IIn supernova progenitors within decades before their explosion |doi-access=free |journal=Monthly Notices of the Royal Astronomical Society |language=en |volume=439 |issue=3 |pages=2917–2926 |bibcode=2014MNRAS.439.2917M |arxiv=1401.4893 |doi=10.1093/mnras/stu163 |issn=1365-2966}}</ref> Type Ic supernovae have been observed to occur in regions that are more metal-rich and have higher star-formation rates than average for their host galaxies.<ref>{{Cite journal |last1=Galbany |first1=L. |last2=Anderson |first2=J. P. |last3=Sánchez |first3=S. F. |last4=Kuncarayakti |first4=H. |last5=Pedraz |first5=S. |last6=González-Gaitán |first6=S. |last7=Stanishev |first7=V. |last8=Domínguez |first8=I. |last9=Moreno-Raya |first9=M. E. |last10=Wood-Vasey |first10=W. M. |last11=Mourão |first11=A. M. |last12=Ponder |first12=K. A. |last13=Badenes |first13=C. |last14=Mollá |first14=M. |last15=López-Sánchez |first15=A. R. |date=13 March 2018 |title=PISCO: The PMAS/PPak Integral-field Supernova Hosts Compilation |doi-access=free |journal=The Astrophysical Journal |volume=855 |issue=2 |pages=107 |doi=10.3847/1538-4357/aaaf20 |bibcode=2018ApJ...855..107G |arxiv=1802.01589 |issn=1538-4357}}</ref> The table shows the progenitor for the main types of core collapse supernova, and the approximate proportions that have been observed in the local neighbourhood.
{|class="wikitable"
|+ Fraction of core collapse supernovae types by progenitor<ref name=eldridge/>
|-
! Type !! Progenitor star !! Fraction
|-
|Ib ||WC [[Wolf–Rayet star|Wolf–Rayet]] or [[helium star]] ||9.0%
|-
|Ic ||WO [[Wolf–Rayet star|Wolf–Rayet]] ||17.0%
|-
|II-P ||[[Supergiant]] ||55.5%
|-
|II-L ||[[Supergiant]] with a depleted hydrogen shell ||3.0%
|-
|IIn ||[[Supergiant]] in a dense cloud of expelled material (such as [[Luminous blue variable|LBV]])||2.4%
|-
|IIb ||[[Supergiant]] with highly depleted hydrogen (stripped by companion?) ||12.1%
|-
|IIpec ||[[Blue supergiant]]||1.0%
|}

[[File:Supernovae as initial mass-metallicity.svg|upright=1.8|thumb|Supernova types by initial mass-metallicity]]
[[File:Remnants of single massive stars.svg|upright=1.8|thumb|Remnants of single massive stars]]

There are a number of difficulties reconciling modelled and observed stellar evolution leading up to core collapse supernovae. Red supergiants are the progenitors for the vast majority of core collapse supernovae, and these have been observed but only at relatively low masses and luminosities, below about {{solar mass|18}} and {{solar luminosity|100,000}}, respectively. Most progenitors of type II supernovae are not detected and must be considerably fainter, and presumably less massive. This discrepancy has been referred to as the '''red supergiant problem'''.<ref name="davies2020"/> It was first described in 2009 by Stephen Smartt, who also coined the term. After performing a volume-limited search for supernovae, Smartt et al. found the lower and upper mass limits for type II-P supernovae to form to be {{solar mass|{{val|8.5|1|1.5}}}} and {{solar mass|{{val|16.5|1.5}}}}, respectively. The former is consistent with the expected upper mass limits for white dwarf progenitors to form, but the latter is not consistent with massive star populations in the Local Group.<ref name=smartt2009>{{Cite journal |last1=Smartt |first1=S. J. |last2=Eldridge |first2=J. J. |last3=Crockett |first3=R. M. |last4=Maund |first4=J. R. |date=May 2009 |title=The death of massive stars – I. Observational constraints on the progenitors of Type II-P supernovae |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=395 |issue=3 |pages=1409–1437 |arxiv=0809.0403 |bibcode=2009MNRAS.395.1409S |doi=10.1111/j.1365-2966.2009.14506.x |doi-access=free |s2cid=3228766 |issn=0035-8711}}</ref> The upper limit for red supergiants that produce a visible supernova explosion has been calculated at {{val|19|4|2|u=solar mass}}.<ref name=davies2020>{{cite journal |bibcode=2020MNRAS.496L.142D |arxiv=2005.13855 |doi=10.1093/mnrasl/slaa102 |title='On the red supergiant problem': A rebuttal, and a consensus on the upper mass cut-off for II-P progenitors |year=2020 |last1=Davies |first1=Ben |last2=Beasor |first2=Emma R. |journal=Monthly Notices of the Royal Astronomical Society: Letters |volume=496 |issue=1 |pages=L142–L146 |doi-access=free }}</ref>

It is thought that higher mass red supergiants do not explode as supernovae, but instead evolve back towards hotter temperatures. Several progenitors of type IIb supernovae have been confirmed, and these were K and G supergiants, plus one A supergiant.<ref name=smartt/> Yellow hypergiants or LBVs are proposed progenitors for type IIb supernovae, and almost all type IIb supernovae near enough to observe have shown such progenitors.<ref name=problem>
{{Cite journal
 |last1=Walmswell |first1=J. J.
 |last2=Eldridge |first2=J. J.
 |doi=10.1111/j.1365-2966.2011.19860.x
 |title=Circumstellar dust as a solution to the red supergiant supernova progenitor problem
 |journal=Monthly Notices of the Royal Astronomical Society
 |volume=419 |issue=3 |pages=2054
 |year=2012
|doi-access=free
 |arxiv=1109.4637
 |bibcode=2012MNRAS.419.2054W
|s2cid=118445879
 }}</ref><ref name=ysg>
{{Cite journal
 |last1=Georgy |first1=C.
 |doi=10.1051/0004-6361/201118372
 |title=Yellow supergiants as supernova progenitors: An indication of strong mass loss for red supergiants?
 |journal=Astronomy & Astrophysics
 |volume=538 |pages=L8–L2 |year=2012
|arxiv=1111.7003 |bibcode=2012A&A...538L...8G
|s2cid=55001976
 }}</ref>
[[File:Stellar evolution v2024.png|alt=Infographic showing arrows between circles representing stellar evolution and how it varies by mass|thumb|Approximate stellar evolution pathways of supernova progenitor stars (and lower mass stars) with circle size reflecting relative size and color related to temperature]]
Blue supergiants form an unexpectedly high proportion of confirmed supernova progenitors, partly due to their high luminosity and easy detection, while not a single Wolf–Rayet progenitor has yet been clearly identified.<ref name=smartt>
{{cite journal
|bibcode=2009ARA&A..47...63S
|title=Progenitors of Core-Collapse Supernovae
|journal=[[Annual Review of Astronomy & Astrophysics]]
|volume=47 |issue=1 |pages=63–106
|year=2009 |doi=10.1146/annurev-astro-082708-101737
|arxiv=0908.0700
|last1=Smartt
|first1=Stephen J.
|last2=Thompson
|first2=Todd A.
|last3=Kochanek
|first3=Christopher S.
|s2cid=55900386
}}</ref><ref name=yoon/> Models have had difficulty showing how blue supergiants lose enough mass to reach supernova without progressing to a different evolutionary stage. One study has shown a possible route for low-luminosity post-red supergiant luminous blue variables to collapse, most likely as a type IIn supernova.<ref name=lbv>
{{Cite journal
 |last1=Groh |first1=J. H.
 |last2=Meynet |first2=G.
 |last3=Ekström |first3=S.
 |title=Massive star evolution: Luminous blue variables as unexpected supernova progenitors
 |doi=10.1051/0004-6361/201220741
 |journal=Astronomy & Astrophysics
 |volume=550 |pages=L7 |year=2013
|arxiv=1301.1519
 |bibcode=2013A&A...550L...7G
|s2cid=119227339
 }}</ref> Several examples of hot luminous progenitors of type IIn supernovae have been detected: [[SN 2005gy]] and [[SN 2010jl]] were both apparently massive luminous stars, but are very distant; and [[SN 2009ip]] had a highly luminous progenitor likely to have been an LBV, but is a peculiar supernova whose exact nature is disputed.<ref name=smartt/>

The progenitors of type Ib/c supernovae are not observed at all, and constraints on their possible luminosity are often lower than those of known [[WC star]]s.<ref name=smartt/> [[WO star]]s are extremely rare and visually relatively faint, so it is difficult to say whether such progenitors are missing or just yet to be observed. Very luminous progenitors have not been securely identified, despite numerous supernovae being observed near enough that such progenitors would have been clearly imaged.<ref name=yoon>
{{cite journal
|bibcode=2012A&A...544L..11Y
|title=On the nature and detectability of Type Ib/c supernova progenitors
|journal=Astronomy & Astrophysics
|volume=544|pages=L11
|year=2012
|doi=10.1051/0004-6361/201219790
|arxiv=1207.3683|last1=Yoon
|first1=S.-C.
|last2=Gräfener
|first2=G.
|last3=Vink
|first3=J. S.
|last4=Kozyreva
|first4=A.
|last5=Izzard
|first5=R. G.
|s2cid=118596795
}}</ref> Population modelling shows that the observed type Ib/c supernovae could be reproduced by a mixture of single massive stars and stripped-envelope stars from interacting binary systems.<ref name=eldridge/> The continued lack of unambiguous detection of progenitors for normal type Ib and Ic supernovae may be due to most massive stars collapsing directly to a black hole [[failed supernova|without a supernova outburst]]. Most of these supernovae are then produced from lower-mass low-luminosity helium stars in binary systems. A small number would be from rapidly rotating massive stars, likely corresponding to the highly energetic type Ic-BL events that are associated with long-duration gamma-ray bursts.<ref name=smartt/>