Editing Supernova (section)

====Type II====
{{Main|Type II supernova}}
[[Image:SN 1997D.jpg|thumb|The atypical subluminous type II [[SN 1997D]]]]
Stars with initial masses less than about {{Solar mass|8}} never develop a core large enough to collapse and they eventually lose their atmospheres to become white dwarfs. Stars with at least {{Solar mass|9}} (possibly as much as {{Solar mass|12}}<ref name="superagb">
{{Cite journal
 |last1=Poelarends |first1=A. J. T.
 |last2=Herwig |first2=F.
 |last3=Langer |first3=N.
 |last4=Heger |first4=A.
 |year=2008
 |title=The Supernova Channel of Super-AGB Stars
 |journal=[[The Astrophysical Journal]]
 |volume=675 |issue=1|pages=614–625
 |arxiv=0705.4643
 |bibcode=2008ApJ...675..614P
 |doi=10.1086/520872
|s2cid=18334243
 }}</ref>) evolve in a complex fashion, progressively burning heavier elements at hotter temperatures in their cores.<ref name="WoosleyJanka">
{{Cite journal
 |last1=Woosley |first1=S. E.
 |last2=Janka |first2=H.-T.
 |date=2005
 |title=The Physics of Core-Collapse Supernovae
 |journal=[[Nature Physics]]
 |volume=1 |issue=3 |pages=147–154
 |arxiv=astro-ph/0601261
 |bibcode=2005NatPh...1..147W
 |citeseerx=10.1.1.336.2176
 |doi=10.1038/nphys172
|s2cid=118974639
 }}</ref><ref name="science304">
{{cite journal
 |last1=Gilmore |first1=G.
 |year=2004
 |title=The Short Spectacular Life of a Superstar
 |journal=[[Science (journal)|Science]]
 |volume=304 |issue=5679 |pages=1915–1916
 |doi=10.1126/science.1100370
 |pmid=15218132
|s2cid=116987470
 }}</ref> The star becomes layered like an onion, with the burning of more easily fused elements occurring in larger shells.<ref name=heger/><ref name="hinshaw">
{{cite book
 |last1=Faure |first1=G.
 |last2=Mensing |first2=T. M.
 |year=2007
 |chapter=Life and Death of Stars
 |title=Introduction to Planetary Science
 |pages=35–48
 |doi=10.1007/978-1-4020-5544-7_4
 |isbn=978-1-4020-5233-0
}}</ref> Although popularly described as an onion with an iron core, the least massive supernova progenitors only have oxygen-[[neon]](-[[magnesium]]) cores. These [[super-AGB star]]s may form the majority of core collapse supernovae, although less luminous and so less commonly observed than those from more massive progenitors.<ref name="superagb"/>

If core collapse occurs during a supergiant phase when the star still has a hydrogen envelope, the result is a type II supernova.<ref name=Horiuchi_et_al_2014>{{cite journal |bibcode=2014MNRAS.445L..99H |arxiv=1409.0006 |doi=10.1093/mnrasl/slu146|title=The red supergiant and supernova rate problems: Implications for core-collapse supernova physics |year=2014 |last1=Horiuchi |first1=S. |last2=Nakamura |first2=K. |last3=Takiwaki |first3=T. |last4=Kotake |first4=K. |last5=Tanaka |first5=M. |journal=Monthly Notices of the Royal Astronomical Society: Letters |volume=445 |pages=L99–L103 |doi-access=free }}</ref> The rate of mass loss for luminous stars depends on the metallicity and [[luminosity]]. Extremely luminous stars at near solar metallicity will lose all their hydrogen before they reach core collapse and so will not form a supernova of type II.<ref name=Horiuchi_et_al_2014/> At low metallicity, all stars will reach core collapse with a hydrogen envelope but sufficiently massive stars collapse directly to a black hole without producing a visible supernova.<ref name="heger"/>

Stars with an initial mass up to about 90 times the Sun, or a little less at high metallicity, result in a type II-P supernova, which is the most commonly observed type. At moderate to high metallicity, stars near the upper end of that mass range will have lost most of their hydrogen when core collapse occurs and the result will be a type II-L supernova.<ref>{{cite journal |doi=10.1093/mnras/stu1760 |bibcode=2014MNRAS.445..554F |arxiv=1409.1536 |title=A sample of Type II-L supernovae |year=2014 |last1=Faran |first1=T. |last2=Poznanski |first2=D. |last3=Filippenko |first3=A. V. |last4=Chornock |first4=R. |last5=Foley |first5=R. J. |last6=Ganeshalingam |first6=M. |last7=Leonard |first7=D. C. |last8=Li |first8=W. |last9=Modjaz |first9=M. |last10=Serduke |first10=F. J. D. |last11=Silverman |first11=J. M. |journal=Monthly Notices of the Royal Astronomical Society |volume=445 |issue=1 |pages=554–569 |doi-access=free }}</ref> At very low metallicity, stars of around {{Solar mass|140–250}} will reach core collapse by pair instability while they still have a hydrogen atmosphere and an oxygen core and the result will be a supernova with type II characteristics but a very large mass of ejected <sup>56</sup>Ni and high luminosity.<ref name="heger"/><ref>{{cite journal|title=Mind the Gap: The Location of the Lower Edge of the Pair-instability Supernova Black Hole Mass Gap |first1=R. |last1=Farmer |first2=M. |last2=Renzo |first3=S. E. |last3=de Mink |first4=P. |last4=Marchant |first5=S. |last5=Justham |doi=10.3847/1538-4357/ab518b |bibcode=2019ApJ...887...53F |arxiv=1910.12874 |journal=The Astrophysical Journal |year=2019 |volume=887 |number=1 |page=53 |doi-access=free }}</ref>