# Hypernova

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{{short description|Supernova that ejects a large mass at unusually high velocity}}
{{Other uses|Hypernova (disambiguation)}}
[[File:SN 1998bw.jpg|thumb|upright=1.4|[ESO](/source/European_Southern_Observatory) image of [SN 1998bw](/source/SN_1998bw), believed by some astronomers to be a hypernova,<ref name=grb980425>{{cite web
 | title=Gamma-ray burst 980425
 | first=Jochen | last=Greiner
 | publisher=Max-Planck-Institute for Extraterrestrial Physics
 | url=http://www.mpe.mpg.de/~jcg/grb980425.html
 | accessdate=2017-06-11 }}</ref> in a spiral arm of galaxy [ESO 184-G82](/source/ESO_184-G82).]]
A '''hypernova''' is a very energetic [supernova](/source/supernova) which is believed to result from an extreme core collapse scenario. In this case, a massive star (>30 [solar mass](/source/solar_mass)es) collapses to form a [rotating black hole](/source/rotating_black_hole) emitting twin astrophysical jets and surrounded by an [accretion disk](/source/accretion_disk). It is a type of [stellar explosion](/source/stellar_explosion) that ejects material with an unusually high [kinetic energy](/source/kinetic_energy), an order of magnitude higher than most supernovae, with a luminosity at least 10 times greater. Hypernovae release such intense [gamma rays](/source/gamma_rays) that they often appear similar to a [Type Ic supernova](/source/Type_Ic_supernova), but with unusually broad spectral lines indicating an extremely high expansion velocity. Hypernovae are one of the mechanisms for producing long [gamma ray bursts (GRBs)](/source/Gamma_ray_burst), which range from 2 seconds to over a minute in duration. They have also been referred to as [superluminous supernova](/source/superluminous_supernova)e, though that classification also includes other types of extremely luminous stellar explosions that have different origins.

==History==

In the 1980s, the term ''hypernova'' was used to describe a theoretical type of supernova now known as a [pair-instability supernova](/source/pair-instability_supernova). It referred to the extremely high energy of the explosion compared to typical [core collapse supernova](/source/core_collapse_supernova)e.<ref name=ww1982/><ref name=janka2012/><ref name=gass1988/> The term had previously been used to describe hypothetical explosions from diverse events such as [hyperstar](/source/Hypergiant)s, extremely massive [population III](/source/population_III) stars in the early universe,<ref name=barrington1963/> or from events such as [black hole](/source/black_hole) mergers.<ref name=park1991/>

In February 1997, Dutch-Italian satellite [BeppoSAX](/source/BeppoSAX) was able to trace [GRB 970508](/source/GRB_970508) to a faint galaxy roughly 6 billion light years away.<ref name=bloom1998/> From analyzing the spectroscopic data for both the GRB 970508 and its host galaxy, Bloom et al. concluded in 1998 that a hypernova was the likely cause.<ref name=bloom1998/> That same year, hypernovae were hypothesized in greater detail by Polish astronomer [Bohdan Paczyński](/source/Bohdan_Paczy%C5%84ski) as supernovae from rapidly spinning stars.<ref name=paczynski1997/>

The usage of the term ''hypernova'' from the late 20th century has since been refined to refer to those supernovae with unusually large kinetic energy.<ref name=stevenson2013/>  The first hypernova observed was [SN 1998bw](/source/SN_1998bw), with a luminosity 100 times higher than a standard Type Ib.<ref name=woosley1999/>  This supernova was the first to be associated with a gamma-ray burst (GRB) and it produced a shockwave containing an order of magnitude more energy than a normal supernova.  Other scientists prefer to call these objects simply broad-lined [Type Ic supernova](/source/Type_Ic_supernova)e.<ref name=moriya2018/>  Since then the term has been applied to a variety of objects, not all of which meet the standard definition; for example [ASASSN-15lh](/source/ASASSN-15lh).<ref name=orwig2016/>

In 2023, the observation of the highly energetic, [non-quasar](/source/Quasar) transient event [AT2021lwx](/source/AT2021lwx) was published with an extremely strong emission from [mid-infrared](/source/Infrared) to [X-ray](/source/X-ray) wavelengths and an overall energy of {{val|1.5|e=46|ul=joules}}.<ref>{{Cite journal |title="Multiwavelength observations of the extraordinary accretion event AT2021lwx" |journal=Monthly Notices of the Royal Astronomical Society |year=2023 |doi=10.1093/mnras/stad1000 |last1=Wiseman |first1=P. |last2=Wang |first2=Y. |last3=Hönig |first3=S. |last4=Castro-Segura |first4=N. |last5=Clark |first5=P. |last6=Frohmaier |first6=C. |last7=Fulton |first7=M. D. |last8=Leloudas |first8=G. |last9=Middleton |first9=M. |last10=Müller-Bravo |first10=T. E. |last11=Mummery |first11=A. |last12=Pursiainen |first12=M. |last13=Smartt |first13=S. J. |last14=Smith |first14=K. |last15=Sullivan |first15=M. |last16=Anderson |first16=J. P. |last17=Acosta Pulido |first17=J. A. |last18=Charalampopoulos |first18=P. |last19=Banerji |first19=M. |last20=Dennefeld |first20=M. |last21=Galbany |first21=L. |last22=Gromadzki |first22=M. |last23=Gutiérrez |first23=C. P. |last24=Ihanec |first24=N. |last25=Kankare |first25=E. |last26=Lawrence |first26=A. |last27=Mockler |first27=B. |last28=Moore |first28=T. |last29=Nicholl |first29=M. |last30=Onori |first30=F. |volume=522 |issue=3 |pages=3992–4002 |doi-access=free |display-authors=1 |arxiv=2303.04412 }}</ref>  This object is not thought to be a hypernova; instead, it is likely to be a huge gas cloud being absorbed by a massive black hole. The event was also assigned the random name "ZTF20abrbeie" by the [Zwicky Transient Facility](/source/Zwicky_Transient_Facility). This  name and the seeming ferocity of the event  led to nickname "Scary Barbie", drawing the attention of the mainstream press.[https://www.usatoday.com/story/news/nation/2023/05/12/largest-space-explosion-scary-barbie-black-hole/70212322007/]

==Properties==
Hypernovae are thought to be supernovae with ejecta having a kinetic energy larger than about {{val|e=45|u=joule}}, an order of magnitude higher than a typical core collapse supernova. The ejected nickel masses are large and the ejection velocity up to 99% of the [speed of light](/source/speed_of_light). These are typically of Type Ic, and some are associated with long-duration [gamma-ray bursts](/source/gamma-ray_bursts). The [electromagnetic](/source/electromagnetic) energy released by these events varies from comparable to other Type Ic supernova, to some of the most luminous supernovae known such as [SN 1999as](/source/SN_1999as).<ref name=nomoto2003/><ref name=mazzali2005/>

The archetypal hypernova, SN 1998bw, was associated with [GRB 980425](/source/GRB_980425). Its spectrum showed no hydrogen and no clear [helium](/source/helium) features, but strong silicon lines identified it as a Type Ic supernova. The main [absorption line](/source/absorption_line)s were extremely broadened and the light curve showed a very rapid brightening phase, reaching the brightness of a [Type Ia supernova](/source/Type_Ia_supernova) at day 16. The total ejected mass was about {{solar mass|10}} and the mass of nickel ejected about {{solar mass|0.4}}.<ref name=nomoto2003/> All supernovae associated with GRBs have shown the high-energy ejecta that characterises them as hypernovae.<ref name=mosta2014/>

Unusually bright [radio supernova](/source/radio_supernova)e have been observed as counterparts to hypernovae, and have been termed "radio hypernovae".<ref name=nakuchi2015/>

==Astrophysical models ==
Models for hypernovae focus on the efficient transfer of energy into the ejecta. In normal [core collapse supernova](/source/core_collapse_supernova)e, 99% of [neutrinos](/source/Neutrino) generated in the collapsing core escape without driving the ejection of material. It is thought that rotation of the supernova progenitor drives a jet that accelerates material away from the explosion at close to the speed of light. Binary systems are increasingly being studied as the best method for both stripping stellar envelopes to leave a bare carbon-oxygen core, and for inducing the necessary spin conditions to drive a hypernova.

===Collapsar model===
{{for|a completely collapsed star|stellar black hole}}
The collapsar model describes a type of supernova that produces a gravitationally collapsed object, or [black hole](/source/black_hole). The word "collapsar", short for "collapsed [star](/source/star)", was formerly used to refer to the end product of stellar [gravitational collapse](/source/gravitational_collapse), a [stellar-mass black hole](/source/stellar_black_hole). The word is now sometimes used to refer to a specific model for the collapse of a fast-rotating star. When core collapse occurs in a star with a core at least around fifteen times the [Sun's mass](/source/Solar_mass) ({{Solar mass}})—though chemical composition and rotational rate are also significant—the explosion energy is insufficient to expel the outer layers of the star, and it will collapse into a black hole without producing a visible supernova outburst.

A star with a core mass slightly below this level—in the range of {{Solar mass|5–15}}—will undergo a supernova explosion, but so much of the ejected mass falls back onto the core remnant that it still collapses into a black hole. If such a star is rotating slowly, then it will produce a faint supernova, but if the star is rotating quickly enough, then the fallback to the black hole will produce [relativistic jets](/source/Astrophysical_jet). Those powerful jets plough through stellar material creating strong shock waves, with the vigorous winds of newly-formed [<sup>56</sup>Ni](/source/Nickel) blowing off the accretion disk, detonating the hypernova explosion. The ejected radioactive decay of <sup>56</sup>Ni renders the visible outburst substantially more luminous than a standard supernova.<ref>{{Cite web |title=Hypernova {{!}} COSMOS |url=https://astronomy.swin.edu.au/cosmos/H/Hypernova |access-date=2024-07-05 |website=astronomy.swin.edu.au}}</ref> The jets also beam high energy particles and gamma rays directly outward and thereby produce [x-ray](/source/x-ray) or [gamma-ray](/source/Gamma_ray) bursts; the jets can last for several seconds or longer and correspond to long-duration gamma-ray bursts, but they do not appear to explain short-duration gamma-ray bursts.<ref name=nomoto2009/><ref name=fujimoto2008/>

===Binary models===
The mechanism for producing the stripped progenitor, a carbon-oxygen star lacking any significant hydrogen or helium, of Type Ic supernovae was once thought to be an extremely evolved massive star, for example a type WO [Wolf-Rayet star](/source/Wolf-Rayet_star) whose dense [stellar wind](/source/stellar_wind) expelled all its outer layers. Observations have failed to detect any such progenitors. It is still not conclusively shown that the progenitors are actually a different type of object, but several cases suggest that lower-mass "helium giants" are the progenitors. These stars are not sufficiently massive to expel their envelopes simply by stellar winds, and they would be stripped by mass transfer to a binary companion. Helium giants are increasingly favoured as the progenitors of Type Ib supernovae, but the progenitors of Type Ic supernovae is still uncertain.<ref name=tauris2013/>

One proposed mechanism for producing gamma-ray bursts is induced [gravitational collapse](/source/gravitational_collapse), where a [neutron star](/source/neutron_star) is triggered to collapse into a [black hole](/source/black_hole) by the core collapse of a close companion consisting of a stripped carbon-oxygen core. The induced neutron star collapse allows for the formation of jets and high-energy [ejecta](/source/ejecta) that have been difficult to model from a single star.<ref name=ruffini2018/>

==See also==
{{Portal|Astronomy|Stars}}
* {{annotated link|Gamma-ray burst progenitors}}
* {{annotated link|Quark star}}
* {{annotated link|Quark-nova}}

==References==
{{reflist|30em|refs=

<ref name=stevenson2013>{{cite book|author=David S. Stevenson|title=Extreme Explosions: Supernovae, Hypernovae, Magnetars, and Other Unusual Cosmic Blasts|url=https://books.google.com/books?id=r124BAAAQBAJ|date=5 September 2013|publisher=Springer Science & Business Media|isbn=978-1-4614-8136-2|access-date=18 August 2019|archive-date=25 January 2022|archive-url=https://web.archive.org/web/20220125083414/https://books.google.com/books?id=r124BAAAQBAJ|url-status=live}}</ref>

<ref name=moriya2018>{{cite journal |doi=10.1007/s11214-018-0493-6 |title=Superluminous Supernovae |journal=Space Science Reviews |volume=214 |issue=2 |pages=59 |year=2018 |last1=Moriya |first1=Takashi J. |last2=Sorokina |first2=Elena I. |last3=Chevalier |first3=Roger A. |bibcode=2018SSRv..214...59M |arxiv=1803.01875 |s2cid=119199790 }}</ref>

<ref name=orwig2016>{{cite web|url=http://www.businessinsider.com/astronomers-discover-the-most-powerful-hypernova-2016-1|title=Astronomers are baffled by a newly discovered cosmic explosion that shines 570 billion times brighter than the sun|author=Jessica Orwig|website=[Business Insider](/source/Business_Insider)|date=January 14, 2016|access-date=March 22, 2016|archive-date=April 2, 2016|archive-url=https://web.archive.org/web/20160402031204/http://www.businessinsider.com/astronomers-discover-the-most-powerful-hypernova-2016-1|url-status=live}}</ref>

<ref name=bloom1998>{{cite journal|last1=Bloom|title=The Host Galaxy of GRB 970508|journal=The Astrophysical Journal|volume=507|date=1998|issue=507|pages=L25–28|doi=10.1086/311682|arxiv=astro-ph/9807315|bibcode=1998ApJ...507L..25B|s2cid=18107687}}</ref>

<ref name=paczynski1997>{{cite conference|last1=Paczynski|title=GRBs as Hypernovae|conference=Huntsville Gamma-Ray Burst Symposium|year=1997|arxiv=astro-ph/9712123|bibcode=1997astro.ph.12123P}}</ref>

<ref name=woosley1999>{{cite journal|last1=Woosley|title=Gamma-Ray Bursts and Type Ic Supernovae: SN 1998bw|journal=The Astrophysical Journal|volume=516|issue=2|pages=788–796|year=1999|arxiv=astro-ph/9806299|bibcode=1999ApJ...516..788W|doi=10.1086/307131|s2cid=17690696}}</ref>

<ref name=gass1988>{{cite journal |bibcode=1988A&A...189..194G |title=Spectrum analysis of the extremely metal-poor carbon dwarf star G 77-61 |journal=Astronomy and Astrophysics |volume=189 |pages=194 |last1=Gass |first1=H. |last2=Liebert |first2=James |last3=Wehrse |first3=R. |year=1988 }}</ref>

<ref name=barrington1963>{{cite journal |doi=10.1038/198651a0 |title=Preliminary Results from the Very-Low Frequency Receiver Aboard Canada's Alouette Satellite |journal=Nature |volume=198 |issue=4881 |pages=651–656 |year=1963 |last1=Barrington |first1=R. E. |last2=Belrose |first2=J. S. |bibcode=1963Natur.198..651B |s2cid=41012117 }}</ref>

<ref name=park1991>{{cite journal |bibcode=1991ApJ...375..565P |title=Are Hypernovae Detectable? |journal=The Astrophysical Journal |volume=375 |pages=565 |last1=Park |first1=Seok J. |last2=Vishniac |first2=Ethan T. |year=1991 |doi=10.1086/170217 }}</ref>

<ref name=janka2012>{{cite journal |bibcode=2012ARNPS..62..407J |title=Explosion Mechanisms of Core-Collapse Supernovae |journal=[Annual Review of Nuclear and Particle Science](/source/Annual_Review_of_Nuclear_and_Particle_Science) |volume=62 |issue=1 |pages=407–451 |last1=Janka |first1=Hans-Thomas |year=2012 |arxiv=1206.2503 |doi=10.1146/annurev-nucl-102711-094901| doi-access=free |s2cid=118417333 }}</ref>

<ref name=ww1982>{{cite journal |bibcode=1981STIN...8316268W |title=Theoretical models for supernovae |journal=NASA Sti/Recon Technical Report N |volume=83 |pages=16268 |last1=Woosley |first1=S. E. |last2=Weaver |first2=T. A. |year=1981 }}</ref>

<ref name=nomoto2003>{{cite book |bibcode=2004ASSL..302..277N |volume=302 |pages=277–325 |last1=Nomoto |first1=Ken'Ichi |last2=Maeda |first2=Keiichi |last3=Mazzali |first3=Paolo A. |last4=Umeda |first4=Hideyuki |last5=Deng |first5=Jinsong |last6=Iwamoto |first6=Koichi |title=Stellar Collapse |chapter=Hypernovae and Other Black-Hole-Forming Supernovae |series=Astrophysics and Space Science Library |year=2004 |arxiv=astro-ph/0308136 |doi=10.1007/978-0-306-48599-2_10 |isbn=978-90-481-6567-4 |s2cid=119421669 }}</ref>

<ref name=mazzali2005>{{cite journal |bibcode=2005ASPC..342..366M |title=The Properties of Hypernovae in Gamma Ray Bursts |journal=1604-2004: Supernovae as Cosmological Lighthouses |volume=342 |pages=366 |last1=Mazzali |first1=P. A. |last2=Nomoto |first2=K. |last3=Deng |first3=J. |last4=Maeda |first4=K. |last5=Tominaga |first5=N. |year=2005 }}</ref>

<ref name=nakuchi2015>{{cite journal |doi=10.1088/0004-637X/805/2/164 |title=Optical Synchrotron Precursors of Radio Hypernovae |journal=The Astrophysical Journal |volume=805 |issue=2 |pages=164 |year=2015 |last1=Nakauchi |first1=Daisuke |last2=Kashiyama |first2=Kazumi |last3=Nagakura |first3=Hiroki |last4=Suwa |first4=Yudai |last5=Nakamura |first5=Takashi |bibcode=2015ApJ...805..164N |arxiv=1411.1603 |s2cid=118228337 }}</ref>

<ref name=mosta2014>{{cite journal |doi=10.1088/2041-8205/785/2/L29 |title=Magnetorotational Core-Collapse Supernovae in Three Dimensions |journal=The Astrophysical Journal |volume=785 |issue=2 |pages=L29 |year=2014 |last1=Mösta |first1=Philipp |last2=Richers |first2=Sherwood |last3=Ott |first3=Christian D. |last4=Haas |first4=Roland |last5=Piro |first5=Anthony L. |last6=Boydstun |first6=Kristen |last7=Abdikamalov |first7=Ernazar |last8=Reisswig |first8=Christian |last9=Schnetter |first9=Erik |bibcode=2014ApJ...785L..29M |arxiv=1403.1230 |s2cid=17989552 }}</ref>

<ref name=fujimoto2008>{{cite journal |last1=Fujimoto |first1=S. I. |last2=Nishimura |first2=N. |last3=Hashimoto |first3=M. A. |doi=10.1086/529416 |title=Nucleosynthesis in Magnetically Driven Jets from Collapsars |journal=The Astrophysical Journal |volume=680 |issue=2 |pages=1350–1358 |year=2008 |arxiv=0804.0969 |bibcode=2008ApJ...680.1350F|s2cid=118559576 }}</ref>

<ref name=nomoto2009>{{cite journal |doi=10.1017/S1743921310000128 |title=Nucleosynthesis of the Elements in Faint Supernovae and Hypernovae |journal=Proceedings of the International Astronomical Union |volume=5 |pages=34–41 |year=2009 |last1=Nomoto |first1=Ken'Ichi |last2=Moriya |first2=Takashi |last3=Tominaga |first3=Nozomu |doi-access=free }}</ref>

<ref name=tauris2013>{{cite journal |doi=10.1088/2041-8205/778/2/L23 |title=ULTRA-STRIPPED TYPE Ic SUPERNOVAE FROM CLOSE BINARY EVOLUTION |journal=The Astrophysical Journal |volume=778 |issue=2 |pages=L23 |year=2013 |last1=Tauris |first1=T. M. |last2=Langer |first2=N. |last3=Moriya |first3=T. J. |last4=Podsiadlowski |first4=Ph. |last5=Yoon |first5=S.-C. |last6=Blinnikov |first6=S. I. |bibcode=2013ApJ...778L..23T |arxiv=1310.6356 |s2cid=50835291 }}</ref>

<ref name=ruffini2018>{{cite journal |doi=10.3847/1538-4357/aaeac8 |title=A GRB Afterglow Model Consistent with Hypernova Observations |journal=The Astrophysical Journal |volume=869 |issue=2 |pages=101 |year=2018 |last1=Ruffini |first1=R. |last2=Karlica |first2=M. |last3=Sahakyan |first3=N. |last4=Rueda |first4=J. A. |last5=Wang |first5=Y. |last6=Mathews |first6=G. J. |last7=Bianco |first7=C. L. |last8=Muccino |first8=M. |bibcode=2018ApJ...869..101R |arxiv=1712.05000 |s2cid=119449351 |doi-access=free }}</ref>

}}

==Further reading==
{{refbegin}}
* {{cite journal |author1=MacFadyen, A. I. |author2=Woosley, S. E. |title=Collapsars: Gamma-Ray Bursts and Explosions in 'Failed Supernovae' |journal=[Astrophysical Journal](/source/Astrophysical_Journal) |date=1999 |volume=524 |issue=1 |pages=262–289 |doi=10.1086/307790 |arxiv=astro-ph/9810274 |bibcode=1999ApJ...524..262M|s2cid=15534333 }}
* {{cite journal |author=Woosley, S. E. |title=Gamma-ray bursts from stellar mass accretion disks around black holes |journal=[Astrophysical Journal](/source/Astrophysical_Journal) |date=1993 |volume=405 |issue=1 |pages=273–277 |doi=10.1086/172359 |bibcode=1993ApJ...405..273W}}
* {{cite journal |author=Piran, T. |title=The Physics of Gamma-Ray Bursts |journal=[Reviews of Modern Physics](/source/Reviews_of_Modern_Physics) |date=2004 |volume=76 |issue=4 |pages=1143–1210 |doi=10.1103/RevModPhys.76.1143 |arxiv=astro-ph/0405503v1 |bibcode=2004RvMP...76.1143P|s2cid=118941182 }}
* {{cite journal |bibcode=2003Natur.423..847H |title=A very energetic supernova associated with the γ-ray burst of 29 March 2003 |journal=Nature |volume=423 |issue=6942 |pages=847–50 |last1=Hjorth |first1=Jens |last2=Sollerman |first2=Jesper |last3=Møller |first3=Palle |last4=Fynbo |first4=Johan P. U. |last5=Woosley |first5=Stan E. |last6=Kouveliotou |first6=Chryssa |last7=Tanvir |first7=Nial R. |last8=Greiner |first8=Jochen |last9=Andersen |first9=Michael I. |last10=Castro-Tirado |first10=Alberto J. |last11=Castro Cerón |first11=José María |last12=Fruchter |first12=Andrew S. |last13=Gorosabel |first13=Javier |last14=Jakobsson |first14=Páll |last15=Kaper |first15=Lex |last16=Klose |first16=Sylvio |last17=Masetti |first17=Nicola |last18=Pedersen |first18=Holger |last19=Pedersen |first19=Kristian |last20=Pian |first20=Elena |last21=Palazzi |first21=Eliana |last22=Rhoads |first22=James E. |last23=Rol |first23=Evert |last24=Van Den Heuvel |first24=Edward P. J. |last25=Vreeswijk |first25=Paul M. |last26=Watson |first26=Darach |last27=Wijers |first27=Ralph A. M. J. |year=2003 |doi=10.1038/nature01750 |pmid=12815425|arxiv = astro-ph/0306347 |s2cid=4405772 |display-authors=9}}
{{refend}}

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Adapted from the Wikipedia article [Hypernova](https://en.wikipedia.org/wiki/Hypernova) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Hypernova?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.
