Editing Supernova (section)

==Observation history==
{{Main|History of supernova observation}}
Compared to a star's entire history, the visual appearance of a supernova is very brief, sometimes spanning several months, so that the chances of observing one with the naked eye are roughly once in a lifetime. Only a tiny fraction of the 100&nbsp;[[billion]] stars in a typical [[galaxy]] have the capacity to become a supernova, the ability being restricted to those having high mass and those in rare kinds of [[binary star system]]s with at least one [[white dwarf]].<ref>
{{Cite book |last1=Murdin |first1=P. |url=https://archive.org/details/supernovae00murd/page/1 |title=Supernovae |last2=Murdin |first2=L. |publisher=Press Syndicate of the University of Cambridge |year=1978 |isbn=978-0521300384 |location=New York, New York |pages=[https://archive.org/details/supernovae00murd/page/1 1–3] |language=en}}</ref>

===Early discoveries===
The earliest record of a possible supernova, known as HB9, was likely viewed by an unknown prehistoric people of the [[Indian subcontinent]] and recorded on a rock carving in the [[Burzahom archaeological site|Burzahama]] region of [[Kashmir]], dated to {{val|4500|1000|ul=BC}}.<ref name="Joglekar">{{cite journal |last1=Joglekar |first1=H. |last2=Vahia |first2=M. N. |last3=Sule |first3=A. |date=2011 |title=Oldest sky-chart with Supernova record (in Kashmir) |url=http://www.tifr.res.in/~archaeo/papers/Prehistoric%20astronomy/Oldest%20Supernova%20record%20in%20Kashmir.pdf |url-status=live |journal=Purātattva: Journal of the Indian Archaeological Society |issue=41 |pages=207–211 |archive-url=https://web.archive.org/web/20190510190932/http://www.tifr.res.in/~archaeo/papers/Prehistoric%20astronomy/Oldest%20Supernova%20record%20in%20Kashmir.pdf |archive-date=10 May 2019 |access-date=29 May 2019}}</ref> Later, [[SN 185]] was documented by [[Chinese astronomy|Chinese astronomers]] in 185 AD. The brightest recorded supernova was [[SN 1006]], which was observed in AD 1006 in the constellation of [[Lupus (constellation)|Lupus]]. This event was described by observers in China, Japan, Iraq, Egypt and Europe.<ref name="Murdin">
{{cite book |last1=Murdin |first1=Paul |url=https://archive.org/details/supernovae00murd |title=Supernovae |last2=Murdin |first2=Lesley |date=1985 |publisher=[[Cambridge University Press]] |isbn=978-0521300384 |pages=[https://archive.org/details/supernovae00murd/page/14 14]–16 |url-access=registration}}</ref><ref>
{{cite book |last=Burnham |first=Robert Jr. |title=The Celestial handbook |title-link=Celestial handbook |publisher=Dover |year=1978 |pages=[https://archive.org/details/burnhamscelestia02burn/page/1117 1117–1122] |author-link=Robert Burnham Jr.}}</ref><ref name="winkler">
{{cite journal |last1=Winkler |first1=P. F. |last2=Gupta |first2=G. |last3=Long |first3=K. S. |year=2003 |title=The SN 1006 Remnant: Optical Proper Motions, Deep Imaging, Distance, and Brightness at Maximum |journal=[[Astrophysical Journal]] |volume=585 |issue=1 |pages=324–335 |arxiv=astro-ph/0208415 |bibcode=2003ApJ...585..324W |doi=10.1086/345985 |s2cid=1626564}}</ref> The widely observed supernova [[SN 1054]] produced the [[Crab Nebula]].<ref name=":0">{{cite book|url=https://openstax.org/books/astronomy-2e/pages/23-3-supernova-observations |title=Astronomy 2e |last=Fraknoi |first=Andrew |display-authors=etal |publisher=OpenStax |year=2022 |isbn=978-1-951-69350-3 |page=767}}</ref>

Supernovae [[SN 1572]] and [[SN 1604]], the latest Milky Way supernovae to be observed with the naked eye, had a notable influence on the development of astronomy in [[Europe]] because they were used to argue against the [[Aristotle|Aristotelian]] idea that the universe beyond the Moon and planets was static and unchanging.<ref>
{{cite conference |last1=Clark |first1=D. H. |last2=Stephenson |first2=F. R. |date=1982 |title=The Historical Supernovae |location=Dordrecht |publisher=[[D. Reidel]] |pages=355–370 |bibcode=1982ASIC...90..355C |book-title=Supernovae: A survey of current research; Proceedings of the Advanced Study Institute, Cambridge, England, 29 June – 10 July 1981}}</ref> [[Johannes Kepler]] began observing SN 1604 at its peak on 17 October 1604, and continued to make estimates of its brightness until it faded from naked eye view a year later.<ref name="kepler">
{{cite journal |last1=Baade |first1=W. |year=1943 |title=No. 675. Nova Ophiuchi of 1604 as a supernova |journal=Contributions from the Mount Wilson Observatory / Carnegie Institution of Washington |volume=675 |pages=1–9 |bibcode=1943CMWCI.675....1B}}</ref> It was the second supernova to be observed in a generation, after [[Tycho Brahe]] observed SN 1572 in [[Cassiopeia A|Cassiopeia]].<ref name="history">{{cite book |last1=Motz |first1=L. |url=https://books.google.com/books?id=sj4qswEACAAJ&q=the+story+of+astronomy+motz |title=The Story of Astronomy |last2=Weaver |first2=J. H. |date=2001 |publisher=[[Basic Books]] |isbn=978-0-7382-0586-1 |page=76 }}</ref>

There is some evidence that the youngest known supernova in our galaxy, [[G1.9+0.3]], occurred in the late 19th century, considerably more recently than [[Cassiopeia A]] from around 1680.<ref name="chakraborti">
{{cite journal |last1=Chakraborti |first1=S. |last2=Childs |first2=F. |last3=Soderberg |first3=A. |author3-link= Alicia M. Soderberg |date=25 February 2016 |title=Young Remnants of type Ia Supernovae and Their Progenitors: A Study Of SNR G1.9+0.3 |journal=The Astrophysical Journal |volume=819 |issue=1 |page=37 |arxiv=1510.08851 |bibcode=2016ApJ...819...37C |doi=10.3847/0004-637X/819/1/37 |s2cid=119246128 |doi-access=free }}</ref> Neither was noted at the time. In the case of G1.9+0.3, high [[Extinction (astronomy)|extinction]] from dust along the plane of the galactic disk could have dimmed the event sufficiently for it to go unnoticed. The situation for Cassiopeia A is less clear; infrared [[light echo]]es have been detected showing that it was not in a region of especially high extinction.<ref name="krause">
{{cite journal |last=Krause |first=O. |date=2008 |title=The Cassiopeia A Supernova was of type IIb |journal=[[Science (journal)|Science]] |volume=320 |issue=5880 |pages=1195–1197 |arxiv=0805.4557 |bibcode=2008Sci...320.1195K |doi=10.1126/science.1155788 |pmid=18511684 |s2cid=40884513}}</ref>
{{multiple image
 |align=right
 |direction=vertical
 |width=200
 |image1=Crab Nebula.jpg
 |alt1=
 |caption1=The [[Crab Nebula]] is a [[pulsar wind nebula]] associated with the [[1054 supernova]].
 |image2=Chinese report of guest star identified as the supernova of 1054 (SN 1054) in the Lidai mingchen zouyi (历代名臣奏议).jpg
 |alt2=
 |caption2=A 1414 text cites a 1055 report: since "the baleful star appeared, a full year has passed and until now its brilliance has not faded".<ref>{{cite journal |bibcode=2006JAHH....9...77P |title=Notes on translations of the East Asian records relating to the supernova of AD 1054 |last1=Pankenier |first1=David W. |journal=Journal of Astronomical History and Heritage |year=2006 |volume=9 |issue=1 |page=77 |doi=10.3724/SP.J.1440-2807.2006.01.06 |s2cid=54914821 }}</ref>
}}

{| class="wikitable float-right"
|+ Historical supernovae in the Local Group
|-
!year
!observed in
! style="width:6em" |maximum apparent brightness
!certainty<ref>{{cite web | title=SNRcat – High Energy Observations of Galactic Supernova Remnants | publisher=University of Manitoba | url=http://snrcat.physics.umanitoba.ca/ | access-date=16 October 2020 }}</ref> of the<br/>SN's identification
|-
| style="text-align:right" |[[SN 185|185]]
|constellation of [[Centaurus]]
| style="text-align:center" |−6'''<sup>[[Apparent magnitude|m]]</sup>'''
|possible SN, but may be a comet<ref>{{cite journal | first1=Y.-N. | last1=Chin | first2=Y.-L. | last2=Huang | journal=Nature | title=Identification of the guest star of AD 185 as a comet rather than a supernova | volume=371 | issue=6496 | pages=398–399 | issn=0028-0836 | date=September 1994 | language=de | doi=10.1038/371398a0 | bibcode=1994Natur.371..398C | s2cid=4240119 | url=http://www.nature.com/articles/371398a0 | access-date=8 November 2021
}}</ref><ref>{{cite journal | first1=Fu-Yuan | last1=Zhao | first2=R. G. | last2=Strom | first3=Shi-Yang | last3=Jiang | periodical=Chinese Journal of Astronomy and Astrophysics | title=The Guest Star of AD185 must have been a Supernova | volume=6 | issue=5 | pages=635–640 | issn=1009-9271 | date=October 2006 | language=de | doi=10.1088/1009-9271/6/5/17 | bibcode=2006ChJAA...6..635Z | doi-access=free }}</ref>
|-
| style="text-align:right" |[[SN 386|386]]
|constellation of [[Sagittarius (constellation)|Sagittarius]]
| style="text-align:center" | +1.5'''<sup>m</sup>'''<ref>{{cite book | first=Patrick | last=Moore | title=The Data Book of Astronomy | publisher=CRC Press | year=2000 | pages=295–296 | isbn=978-1-4200-3344-1 | url=https://books.google.com/books?id=fDDpBwAAQBAJ&pg=PA295 }}</ref>
|uncertain whether SN or classical nova<ref name="Hoffmann-2020">{{cite journal | first1=Susanne M. | last1=Hoffmann | first2=Nikolaus | last2=Vogt | journal=Monthly Notices of the Royal Astronomical Society | title=A search for the modern counterparts of the Far Eastern guest stars 369 CE, 386 CE and 393 CE | volume=497 | issue=2 | pages=1419–1433 | bibcode=2020MNRAS.497.1419H | date=1 July 2020 | language=de | doi=10.1093/mnras/staa1970 | doi-access=free | arxiv=2007.01013 }}</ref>
|-
| style="text-align:right" |[[SN 393|393]]
|constellation of [[Scorpius]]
| style="text-align:center" |−3'''<sup>m</sup>'''
|possible SN<ref name="Hoffmann-2020"/>
|-
| style="text-align:right" |[[SN 1006|1006]]
|constellation of [[Lupus (constellation)|Lupus]]
| style="text-align:center" |−7.5{{±|0.4}}'''<sup>m</sup>'''<ref>{{citation | first1=P. Frank | last1=Winkler | first2=G. | last2=Gupta | journal=[[The Astrophysical Journal]] | title=The SN 1006 Reminant: Optical Proper Motions, Deep Imaging, Distance, and Brightness at Maximum | volume=585 | pages=324–335 | date=2003 | issue=1 | language=de | doi=10.1086/345985 | arxiv=astro-ph/0208415 | bibcode=2003ApJ...585..324W | s2cid=1626564 }}</ref>
|certain: [[Supernova remnant|SNR]] known
|-
| style="text-align:right" |[[SN 1054|1054]]
|constellation of [[Taurus (constellation)|Taurus]]
| style="text-align:center" |−6'''<sup>m</sup>'''
|certain: SNR and pulsar known
|-
| style="text-align:right" |[[SN 1181|1181]]
|constellation of [[Cassiopeia (constellation)|Cassiopeia]]
| style="text-align:center" |−2'''<sup>m</sup>'''
|likely type Iax SN associated with the remnant Pa30<ref>{{citation | first1=Andreas | last1=Ritter | first2=Quentin A. | last2=Parker | first3=Foteini | last3=Lykou | first4=Albert A. | last4=Zijlstra | first5=Martín A. | last5=Guerrero | journal=The Astrophysical Journal Letters | title=The Remnant and Origin of the Historical Supernova 1181 AD | volume=918 | issue=2 | page=L33 | issn=2041-8205 | date=1 September 2021 | language=de | doi=10.3847/2041-8213/ac2253 | arxiv=2105.12384 | bibcode=2021ApJ...918L..33R | hdl=10261/255617 | s2cid=235195784 | doi-access=free }}</ref>
|-
| style="text-align:right" |[[SN 1572|1572]]
|constellation of [[Cassiopeia (constellation)|Cassiopeia]]
| style="text-align:center" |−4'''<sup>m</sup>'''
|certain: SNR known
|-
| style="text-align:right" |[[Kepler's Supernova|1604]]
|constellation of [[Ophiuchus]]
| style="text-align:center" |−2'''<sup>m</sup>'''
|certain: SNR known
|-
| style="text-align:right" |[[Cassiopeia A|1680]]?
|constellation of [[Cassiopeia (constellation)|Cassiopeia]]
| style="text-align:center" | +6'''<sup>m</sup>'''
|SNR known, unclear whether the SN was observed
|-
| style="text-align:right" |[[G1.9+0.3|1800–1900]]
|constellation of [[Sagittarius (constellation)|Sagittarius]]
| style="text-align:center" | ?'''<sup>m</sup>'''
|SNR known, but not observed
|-
| style="text-align:right" |[[SN 1885A|1885]]
|[[The Andromeda Galaxy|Andromeda Galaxy]]
| style="text-align:center" | +6'''<sup>m</sup>'''
|certain
|-
| style="text-align:right" |[[SN 1987A|1987]]
|[[Large Magellanic Cloud]]
| style="text-align:center" | +3'''<sup>m</sup>'''
|certain
|}

===Telescope findings===
With the development of the astronomical [[telescope]], observation and discovery of fainter and more distant supernovae became possible. The first such observation was of [[SN 1885A]] in the [[Andromeda Galaxy]]. A second supernova, [[SN 1895B]], was discovered in [[NGC 5253]] a decade later.<ref name=Schaefer1995>{{cite journal
 | title=The Peak Brightness of SN 1895B in NGC 5253 and the Hubble Constant
 | last=Schaefer | first=Bradley E.
 | journal=Astrophysical Journal Letters
 | volume=447 | page=L13 | date=July 1995
 | doi=10.1086/309549 | bibcode=1995ApJ...447L..13S | s2cid=227285055 | doi-access=free }}</ref> Early work on what was originally believed to be simply a new category of [[nova]]e was performed during the 1920s. These were variously called "upper-class Novae", "Hauptnovae", or "giant novae".<ref>{{cite book
 | title=Classifying the Cosmos: How We Can Make Sense of the Celestial Landscape
 | first=Steven J. | last=Dick | year=2019
 | page=191 | isbn=9783030103804
 | publisher=Springer International Publishing
 | url=https://books.google.com/books?id=UymODwAAQBAJ&pg=PA191
}}</ref> The name "supernovae" is thought to have been coined by [[Walter Baade]] and Zwicky in lectures at [[Caltech]] in 1931. It was used, as "super-Novae", in a journal paper published by [[Knut Lundmark]] in 1933,<ref name="baas33_1330">{{cite journal
 |last1=Osterbrock |first1=D. E.
 |year=2001
 |title=Who Coined the Word Supernova? Who First Predicted Neutron Stars?
 |journal=[[Bulletin of the American Astronomical Society]]
 |volume=33 |pages=1330
 |bibcode=2001AAS...199.1501O
}}</ref> and in a 1934 paper by Baade and Zwicky.<ref name="Baade1934">
{{cite journal |last1=Baade |first1=Walter |last2=Zwicky |first2=Fritz |date=1934 |title=On Super-novae |journal=[[Proceedings of the National Academy of Sciences]] |volume=20 |issue=5 |pages=254–259 |bibcode=1934PNAS...20..254B |doi=10.1073/pnas.20.5.254 |pmc=1076395 |pmid=16587881 |doi-access=free}}</ref> By 1938, the hyphen was no longer used and the modern name was in use.<ref>
{{cite book
 |last1=Murdin
 |first1=P.
 |last2=Murdin
 |first2=L.
 |year=1985
 |title=Supernovae
 |page=[https://archive.org/details/supernovae00murd/page/42 42]
 |edition=2nd
 |publisher=[[Cambridge University Press]]
 |isbn=978-0-521-30038-4
 |url=https://archive.org/details/supernovae00murd/page/42
 }}</ref>

American astronomers [[Rudolph Minkowski]] and [[Fritz Zwicky]] developed the modern supernova classification scheme beginning in 1941.<ref>
{{Cite journal
 |last=da Silva |first=L. A. L.
 |date=1993
 |title=The Classification of Supernovae
 |journal=[[Astrophysics and Space Science]]
 |volume=202 |issue=2 |pages=215–236
 |bibcode=1993Ap&SS.202..215D
 |doi=10.1007/BF00626878
|s2cid=122727067
 }}</ref> During the 1960s, astronomers found that the maximum intensities of supernovae could be used as [[standard candles]], hence indicators of astronomical distances.<ref>
{{Cite journal
 |last=Kowal |first=C. T.
 |date=1968
 |title=Absolute magnitudes of supernovae
 |journal=[[Astronomical Journal]]
 |volume=73 |pages=1021–1024
 |bibcode=1968AJ.....73.1021K
 |doi=10.1086/110763
|doi-access=free
 }}</ref> Some of the most distant supernovae observed in 2003 appeared dimmer than expected. This supports the view that the expansion of the [[Accelerating universe|universe is accelerating]].<ref name="Leibundgut">
{{cite journal
 |last1=Leibundgut |first1=B.
 |year=2003
 |title=A cosmological surprise: The universe accelerates
 |journal=Europhysics News
 |volume=32 |issue=4 |pages=121–125
 |bibcode=2001ENews..32..121L
 |doi=10.1051/epn:2001401
|doi-access=free
 }}</ref> Techniques were developed for reconstructing supernovae events that have no written records of being observed. The date of the Cassiopeia A supernova event was determined from light echoes off [[nebula]]e,<ref>
{{Cite journal
 |last=Fabian |first=A. C.
 |date=2008
 |title=A Blast from the Past
 |journal=[[Science (journal)|Science]]
 |volume=320 |issue=5880 |pages=1167–1168
 |doi=10.1126/science.1158538
 |pmid=18511676
|s2cid=206513073
 }}</ref> while the age of supernova remnant [[RX J0852.0-4622]] was estimated from temperature measurements<ref>
{{Cite journal
 |last=Aschenbach |first=B.
 |date=1998
 |title=Discovery of a young nearby supernova remnant
 |journal=[[Nature (journal)|Nature]]
 |volume=396 |issue=6707 |pages=141–142
 |bibcode=1998Natur.396..141A
 |doi=10.1038/24103
|s2cid=4426317
 }}</ref> and the [[gamma ray]] emissions from the radioactive decay of [[titanium-44]].<ref>
{{Cite journal
 |last1=Iyudin |first1=A. F.
 |last2=Schönfelder |first2=V.
 |last3=Bennett |first3=K.
 |last4=Bloemen |first4=H.
 |last5=Diehl |first5=R.
 |last6=Hermsen |first6=W.
 |last7=Lichti |first7=G. G.
 |last8=Van Der Meulen |first8=R. D.
 |last9=Ryan |first9=J.
 |last10=Winkler |first10=C.
 |date=1998
 |title=Emission from <sup>44</sup>Ti associated with a previously unknown Galactic supernova
 |journal=[[Nature (journal)|Nature]]
 |volume=396 |issue=6707 |pages=142–144
 |bibcode=1998Natur.396..142I
 |doi=10.1038/24106
|s2cid=4430526
 }}</ref>

[[File:Jades Deep Field Annotated.png|thumb|upright=1.2|Jades Deep Field. A team of astronomers studying JADES data identified about 80 objects (circled in green) that changed in brightness over time. Most of these objects, known as transients, are the result of exploding stars or supernovae.<ref>{{cite web |title=NASA's Webb Opens New Window on Supernova Science - NASA Science |url=https://science.nasa.gov/missions/webb/nasas-webb-opens-new-window-on-supernova-science |website=science.nasa.gov |date=10 June 2024 |access-date=11 June 2024}}</ref>]]

The most luminous supernova ever recorded is [[ASASSN-15lh]], at a distance of 3.82 [[light-year|gigalight-years]]. It was first detected in June 2015 and peaked at {{solar luminosity|570 billion|link=y}}, which is twice the [[bolometric luminosity]] of any other known supernova.<ref>{{Cite journal
 | last1=Dong | first1=Subo | last2=Shappee | first2=B. J.
 | last3=Prieto | first3=J. L. | last4=Jha | first4=S. W.
 | last5=Stanek | first5=K. Z. | last6=Holoien | first6=T. W. -S.
 | last7=Kochanek | first7=C. S. | last8=Thompson | first8=T. A.
 | last9=Morrell | first9=N. | last10=Thompson | first10=I. B.
 | last11=Basu | first11=U. | last12=Beacom | first12=J. F.
 | last13=Bersier | first13=D. | last14=Brimacombe | first14=J.
 | last15=Brown | first15=J. S. | last16=Bufano | first16=F.
 | last17=Chen | first17=Ping | last18=Conseil | first18=E.
 | last19=Danilet | first19=A. B. | last20=Falco | first20=E.
 | last21=Grupe | first21=D. | last22=Kiyota | first22=S.
 | last23=Masi | first23=G. | last24=Nicholls | first24=B.
 | last25=Olivares E. | first25=F. | last26=Pignata | first26=G.
 | last27=Pojmanski | first27=G. | last28=Simonian | first28=G. V.
 | last29=Szczygiel | first29=D. M. | last30=Woźniak | first30=P. R.
 | title=ASASSN-15lh: A highly super-luminous supernova
 | journal=Science | year=2016 | s2cid=31444274
 | volume=351 | issue=6270 | pages=257–260
 | arxiv=1507.03010 | bibcode=2016Sci...351..257D
 | doi=10.1126/science.aac9613 | pmid=26816375
}}</ref> The nature of this supernova is debated and several alternative explanations, such as tidal disruption of a star by a black hole, have been suggested.<ref>
{{Cite journal
 | title=The superluminous transient ASASSN-15lh as a tidal disruption event from a Kerr black hole
 | last1=Leloudas | first1=G. | last2=Fraser | first2=M.
 | last3=Stone | first3=N. C. | last4=van Velzen | first4=S.
 | last5=Jonker | first5=P. G. | last6=Arcavi | first6=I.
 | last7=Fremling | first7=C. | last8=Maund | first8=J. R.
 | last9=Smartt | first9=S. J. | last10=Krìhler | first10=T.
 | last11=Miller-Jones | first11=J. C. A. | last12=Vreeswijk | first12=P. M.
 | last13=Gal-Yam | first13=A. | last14=Mazzali | first14=P. A.
 | last15=De Cia | first15=A. | last16=Howell | first16=D. A.
 | last17=Inserra | first17=C. | last18=Patat | first18=F.
 | last19=de Ugarte Postigo | first19=A. | last20=Yaron | first20=O.
 | last21=Ashall | first21=C. | last22=Bar | first22=I.
 | last23=Campbell | first23=H. | last24=Chen | first24=T. -W.
 | last25=Childress | first25=M. | last26=Elias-Rosa | first26=N.
 | last27=Harmanen | first27=J. | last28=Hosseinzadeh | first28=G.
 | last29=Johansson | first29=J. | last30=Kangas | first30=T.
 | last31=Kankare | first31=E. | last32=Kim | first32=S.
 | last33=Kuncarayakti | first33=H. | last34=Lyman | first34=J.
 | last35=Magee | first35=M. R. | last36=Maguire | first36=K.
 | last37=Malesani | first37=D. | last38=Mattila | first38=S.
 | last39=McCully | first39=C. V. | last40=Nicholl | first40=M.
 | last41=Prentice | first41=S. | last42=Romero-Cañizales | first42=C.
 | last43=Schulze | first43=S. | last44=Smith | first44=K. W.
 | last45=Sollerman | first45=J. | last46=Sullivan | first46=M.
 | last47=Tucker | first47=B. E. | last48=Valenti | first48=S.
 | last49=Wheeler | first49=J. C. | last50=Young | first50=D. R. | display-authors=1
 | journal=Nature Astronomy | year=2016
 | volume=1 | issue=2 | page=0002
 | arxiv=1609.02927 | bibcode=2016NatAs...1E...2L
 | doi=10.1038/s41550-016-0002 | s2cid=73645264
}}</ref>

[[SN 2013fs]] was recorded three hours after the supernova event on 6 October 2013, by the [[Palomar Transient Factory|Intermediate Palomar Transient Factory]]. This is among the earliest supernovae caught after detonation, and it is the earliest for which spectra have been obtained, beginning six hours after the actual explosion. The star is located in a [[spiral galaxy]] named [[NGC 7610]], 160&nbsp;million light-years away in the constellation of Pegasus.<ref>
{{Cite news
 |last=Sample |first=I.
 |date=13 February 2017
|title=Massive supernova visible millions of light-years from Earth
 |url=https://www.theguardian.com/science/2017/feb/13/massive-supernova-visible-millions-of-light-years-from-earth
 |newspaper=The Guardian
 |access-date=13 February 2017
|url-status=live
 |archive-url=https://web.archive.org/web/20170213172456/https://www.theguardian.com/science/2017/feb/13/massive-supernova-visible-millions-of-light-years-from-earth
 |archive-date=13 February 2017
}}</ref><ref>
{{Cite journal
 |last1=Yaron |first1=O.
 |last2=Perley |first2=D. A.
 |last3=Gal-Yam |first3=A.
 |last4=Groh |first4=J. H.
 |last5=Horesh |first5=A.
 |last6=Ofek |first6=E. O.
 |last7=Kulkarni |first7=S. R.
 |last8=Sollerman |first8=J.
 |last9=Fransson |first9=C.
 |date=13 February 2017
|title=Confined dense circumstellar material surrounding a regular type II supernova
 |journal=Nature Physics
 |volume= 13|issue=5 |pages=510–517
 |arxiv=1701.02596
 |bibcode=2017NatPh..13..510Y
 |doi=10.1038/nphys4025
|s2cid=29600801
 }}</ref>

The supernova [[SN 2016gkg]] was detected by amateur astronomer Victor Buso from [[Rosario]], Argentina, on 20 September 2016.<ref name=AS_Now>{{cite magazine
 |author=Astronomy Now journalist
 |date=23 February 2018
|title=Amateur astronomer makes once-in-lifetime discovery
 |magazine=[[Astronomy Now]]
 |url=https://astronomynow.com/2018/02/23/amateur-astronomer-makes-once-in-lifetime-discovery
 |access-date=15 May 2018
|archive-date=16 May 2018
|archive-url=https://web.archive.org/web/20180516174620/https://astronomynow.com/2018/02/23/amateur-astronomer-makes-once-in-lifetime-discovery/
 |url-status=live
 }}</ref><ref name=NatBuso>
{{cite journal
 |last1=Bersten |first1=M. C.
 |last2=Folatelli |first2=G.
 |last3=García |first3=F.
 |last4=Van Dyk |first4=S. D.
 |last5=Benvenuto |first5=O. G.
 |last6=Orellana |first6=M.
 |last7=Buso |first7=V.
 |last8=Sánchez |first8=J. L.
 |last9=Tanaka |first9=M.
 |last10=Maeda |first10=K.
 |last11=Filippenko |first11=A. V.
 |last12=Zheng |first12=W.
 |last13=Brink |first13=T. G.
 |last14=Cenko |first14=S. B.
 |last15=De Jaeger |first15=T.
 |last16=Kumar |first16=S.
 |last17=Moriya |first17=T. J.
 |last18=Nomoto |first18=K.
 |last19=Perley |first19=D. A.
 |last20=Shivvers |first20=I.
 |last21=Smith |first21=N.
 |date=21 February 2018
|title=A surge of light at the birth of a supernova
 |journal=[[Nature (journal)|Nature]]
 |volume=554 |issue=7693 |pages=497–499
 |arxiv=1802.09360
 |bibcode=2018Natur.554..497B
 |doi=10.1038/nature25151
 |pmid=29469097
|s2cid=4383303
 }}</ref> It was the first time that the initial "shock breakout" from an optical supernova had been observed.<ref name=AS_Now/> The progenitor star has been identified in [[Hubble Space Telescope]] images from before its collapse. Astronomer [[Alex Filippenko]] noted: "Observations of stars in the first moments they begin exploding provide information that cannot be directly obtained in any other way."<ref name=AS_Now/>

===Discovery programs===
[[File:NASA-SNR0519690-ChandraXRayObservatory-20150122.jpg|thumb|[[Supernova remnant]] SNR E0519-69.0 in the [[Large Magellanic Cloud]]]]

Because supernovae are relatively rare events within a galaxy, occurring about three times a century in the Milky Way,<ref name="reynolds">
{{cite journal
 |last1=Reynolds |first1=S. P.
 |last2=Borkowski |first2=K. J.
 |last3=Green |first3=D. A.
 |last4=Hwang |first4=U.
 |last5=Harrus |first5=I. M.
 |last6=Petre |first6=R.
 |year=2008
 |title=The Youngest Galactic Supernova Remnant: G1.9+0.3
 |journal=[[The Astrophysical Journal Letters]]
 |volume=680 |issue=1 |pages=L41–L44
 |arxiv=0803.1487
 |bibcode=2008ApJ...680L..41R
 |doi=10.1086/589570
|s2cid=67766657
 }}</ref> obtaining a good sample of supernovae to study requires regular monitoring of many galaxies. Today, amateur and professional astronomers are finding about two thousand every year, some when near maximum brightness, others on old astronomical photographs or plates. Supernovae in other galaxies cannot be predicted with any meaningful accuracy. Normally, when they are discovered, they are already in progress.<ref>
{{cite journal
 |last1=Colgate |first1=S. A.
 |last2=McKee |first2=C.
 |year=1969
 |title=Early Supernova Luminosity
 |journal=[[The Astrophysical Journal]]
 |volume=157 |pages=623
 |bibcode=1969ApJ...157..623C
 |doi=10.1086/150102
}}</ref> To use supernovae as [[standard candle]]s for measuring distance, observation of their peak luminosity is required. It is therefore important to discover them well before they reach their maximum. [[Amateur astronomy|Amateur astronomers]], who greatly outnumber professional astronomers, have played an important role in finding supernovae, typically by looking at some of the closer galaxies through an [[optical telescope]] and comparing them to earlier photographs.<ref>
{{cite book
 |last1=Zuckerman |first1=B.
 |last2=Malkan |first2=M. A.
 |date=1996
 |title=The Origin and Evolution of the Universe
 |url=https://books.google.com/books?id=G0iR4jpWKN4C&pg=PA68
 |publisher=[[Jones & Bartlett Learning]]
 |page=68
 |isbn=978-0-7637-0030-0
 |url-status=live
 |archive-url=https://web.archive.org/web/20160820024335/https://books.google.com/books?id=G0iR4jpWKN4C&pg=PA68
 |archive-date=20 August 2016
}}</ref>

Toward the end of the 20th century, astronomers increasingly turned to computer-controlled telescopes and [[charge-coupled device|CCDs]] for hunting supernovae. While such systems are popular with amateurs, there are also professional installations such as the [[Katzman Automatic Imaging Telescope]].<ref>
{{cite conference
 |last1=Filippenko |first1=A. V.
 |last2=Li |first2=W.-D.
 |last3=Treffers |first3=R. R.
 |last4=Modjaz |first4=M.
 |year=2001
 |title=The Lick Observatory Supernova Search with the Katzman Automatic Imaging Telescope
 |editor1-last=Paczynski |editor1-first=B.
 |editor2-last=Chen |editor2-first=W.-P.
 |editor3-last=Lemme |editor3-first=C.
 |book-title=Small Telescope Astronomy on Global Scale
 |volume=246 |pages=121
 |series=[[ASP Conference Series]]
 |publisher=[[Astronomical Society of the Pacific]]
 |location=San Francisco
 |bibcode=2001ASPC..246..121F
 |isbn=978-1-58381-084-2
}}</ref> The [[Supernova Early Warning System]] (SNEWS) project uses a network of [[neutrino detector]]s to give early warning of a supernova in the Milky Way galaxy.<ref name="Antonioli-2004">
{{Cite journal
 |last1=Antonioli |first1=P.
 |last2=Fienberg |first2=R. T.
 |last3=Fleurot |first3=F.
 |last4=Fukuda |first4=Y.
 |last5=Fulgione |first5=W.
 |last6=Habig |first6=A.
 |last7=Heise |first7=J.
 |last8=McDonald |first8=A. B.
 |last9=Mills |first9=C.
 |last10=Namba |first10=T.
 |last11=Robinson |first11=L. J.
 |last12=Scholberg |first12=K.|author12-link= Kate Scholberg
 |last13=Schwendener |first13=M.
 |last14=Sinnott |first14=R. W.
 |last15=Stacey |first15=B.
 |last16=Suzuki |first16=Y.
 |last17=Tafirout |first17=R.
 |last18=Vigorito |first18=C.
 |last19=Viren |first19=B.
 |last20=Virtue |first20=C.
 |last21=Zichichi |first21=A.
 |date=2004
 |title=SNEWS: The SuperNova Early Warning System
 |journal=[[New Journal of Physics]]
 |volume=6 |page=114
 |arxiv=astro-ph/0406214
 |bibcode=2004NJPh....6..114A
 |doi=10.1088/1367-2630/6/1/114
|s2cid=119431247
 }}</ref><ref>
{{cite journal
 |last1=Scholberg |first1=K.|author-link= Kate Scholberg
 |year=2000
 |title=SNEWS: The supernova early warning system
 |journal=[[AIP Conference Proceedings]]
 |volume=523 |pages=355–361
 |arxiv=astro-ph/9911359
 |bibcode=2000AIPC..523..355S
 |citeseerx=10.1.1.314.8663
 |doi=10.1063/1.1291879
|s2cid=5803494}}</ref> [[Neutrino]]s are [[subatomic particle]]s that are produced in great quantities by a supernova, and they are not significantly absorbed by the interstellar gas and dust of the galactic disk.<ref>
{{cite journal
 |last1=Beacom |first1=J. F.
 |year=1999
 |title=Supernova neutrinos and the neutrino masses
 |journal=Revista Mexicana de Fisica
 |volume=45 |issue=2 |pages=36
 |arxiv=hep-ph/9901300
 |bibcode=1999RMxF...45...36B
}}</ref>

[[File:A star set to explode.jpg|thumbnail|left|upright=1.2|"A star set to explode", the SBW1 nebula surrounds a massive blue supergiant in the [[Carina Nebula]].]]

Supernova searches fall into two classes: those focused on relatively nearby events and those looking farther away. Because of the [[expansion of the universe]], the distance to a remote object with a known [[emission spectrum]] can be estimated by measuring its [[Doppler shift]] (or [[redshift]]); on average, more-distant objects recede with greater velocity than those nearby, and so have a higher redshift. Thus the search is split between high redshift and low redshift, with the boundary falling around a redshift range of z=0.1–0.3, where z is a dimensionless measure of the spectrum's frequency shift.<ref>
{{cite journal
 |last1=Frieman |first1=J. A.
 |last2=Bassett |first2=B.
 |last3=Becker |first3=A.
 |last4=Choi |first4=C.
 |last5=Cinabro |first5=D.
 |last6=Dejongh |first6=F.
 |last7=Depoy |first7=D. L.
 |last8=Dilday |first8=B.
 |last9=Doi |first9=M.
 |last10=Garnavich |first10=P. M.
 |last11=Hogan |first11=C. J.
 |last12=Holtzman |first12=J.
 |last13=Im |first13=M.
 |last14=Jha |first14=S.
 |last15=Kessler |first15=R.
 |last16=Konishi |first16=K.
 |last17=Lampeitl |first17=H.
 |last18=Marriner |first18=J.
 |last19=Marshall |first19=J. L.
 |last20=McGinnis |first20=D.
 |last21=Miknaitis |first21=G.
 |last22=Nichol |first22=R. C.
 |last23=Prieto |first23=J. L.
 |last24=Riess |first24=A. G.
 |last25=Richmond |first25=M. W.
 |last26=Romani |first26=R.
 |last27=Sako |first27=M.
 |last28=Schneider |first28=D. P.
 |last29=Smith |first29=M.
 |last30=Takanashi |first30=N.
 |display-authors=1
 |year=2008
 |title=The Sloan Digital Sky Survey-Ii Supernova Survey: Technical Summary
 |journal=[[The Astronomical Journal]]
 |volume=135 |issue=1
 |pages=338–347
 |arxiv=0708.2749
 |bibcode=2008AJ....135..338F
 |doi=10.1088/0004-6256/135/1/338
|s2cid=53135988
 }}</ref> 

High redshift searches for supernovae usually involve the observation of supernova light curves. These are useful for standard or calibrated candles to generate [[Hubble diagram]]s and make cosmological predictions. Supernova spectroscopy, used to study the physics and environments of supernovae, is more practical at low than at high redshift.<ref>
{{cite conference
 |last1=Perlmutter |first1=S. A.
 |year=1997
 |title=Scheduled discovery of 7+ high-redshift SNe: First cosmology results and bounds on ''q''<sub>0</sub>
 |editor1-last=Ruiz-Lapuente |editor1-first=P.
 |editor2-last=Canal |editor2-first=R.
 |editor3-last=Isern |editor3-first=J.
 |book-title=Thermonuclear Supernovae, Proceedings of the NATO Advanced Study Institute
 |series=NATO Advanced Science Institutes Series C
 |volume=486 |pages=749
 |publisher=[[Kluwer Academic Publishers]]
 |location=Dordrecth
 |arxiv=astro-ph/9602122
 |bibcode=1997ASIC..486..749P
 |doi=10.1007/978-94-011-5710-0_46
}}</ref><ref>
{{Cite journal
 |last1=Linder |first1=E. V.
 |last2=Huterer |first2=D.
 |date=2003
 |title=Importance of supernovae at ''z'' > 1.5 to probe dark energy
 |journal=[[Physical Review D]]
 |volume=67 |issue=8
 |page=081303
 |arxiv=astro-ph/0208138
 |bibcode=2003PhRvD..67h1303L
 |doi=10.1103/PhysRevD.67.081303
|s2cid=8894913
 }}</ref> Low redshift observations also anchor the low-distance end of the [[Hubble curve]], which is a plot of distance versus redshift for visible galaxies.<ref>
{{Cite journal
 |last1=Perlmutter |first1=S. A.
 |last2=Gabi |first2=S.
 |last3=Goldhaber |first3=G.
 |last4=Goobar |first4=A.
 |last5=Groom |first5=D. E.
 |last6=Hook |first6=I. M.
 |last7=Kim |first7=A. G.
 |last8=Kim |first8=M. Y.
 |last9=Lee |first9=J. C.
 |last10=Pain |first10=R.
 |last11=Pennypacker |first11=C. R.
 |last12=Small |first12=I. A.
 |last13=Ellis |first13=R. S.
 |last14=McMahon |first14=R. G.
 |last15=Boyle |first15=B. J.
 |last16=Bunclark |first16=P. S.
 |last17=Carter |first17=D.
 |last18=Irwin |first18=M. J.
 |last19=Glazebrook |first19=K.
 |last20=Newberg |first20=H. J. M.
 |last21=Filippenko |first21=A. V.
 |last22=Matheson |first22=T.
 |last23=Dopita |first23=M.
 |last24=Couch |first24=W. J.
 |date=1997
 |title=Measurements of the Cosmological Parameters Ω and Λ from the First Seven Supernovae at ''z'' ≥ 0.35
 |journal=[[The Astrophysical Journal]]
 |volume=483 |issue=2 |page=565
 |arxiv=astro-ph/9608192
 |bibcode=1997ApJ...483..565P
 |doi=10.1086/304265
|s2cid=118187050
 }}</ref><ref>{{cite journal
 |last1=Copin
 |first1=Y.
 |last2=Blanc
 |first2=N.
 |last3=Bongard
 |first3=S.
 |last4=Gangler
 |first4=E.
 |last5=Saugé
 |first5=L.
 |last6=Smadja
 |first6=G.
 |last7=Antilogus
 |first7=P.
 |last8=Garavini
 |first8=G.
 |last9=Gilles
 |first9=S.
 |last10=Pain
 |first10=R.
 |last11=Aldering
 |first11=G.
 |last12=Bailey
 |first12=S.
 |last13=Lee
 |first13=B.C.
 |last14=Loken
 |first14=S.
 |last15=Nugent
 |first15=P. E.
 |last16=Perlmutter
 |first16=S. A.
 |last17=Scalzo
 |first17=R.
 |last18=Thomas
 |first18=R.C.
 |last19=Wang
 |first19=L.
 |last20=Weaver
 |first20=B.A.
 |last21=Pécontal
 |first21=E.
 |last22=Kessler
 |first22=R.
 |last23=Baltay
 |first23=C.
 |last24=Rabinowitz
 |first24=D.
 |last25=Bauer
 |first25=A.
 |year=2006
 |title=The Nearby Supernova Factory
 |url=http://www.phyast.pitt.edu/%7Ewmwv/Papers/Wood-Vasey_SNfactory.pdf
 |journal=New Astronomy Reviews
 |volume=50
 |issue=4–5
 |pages=637–640
 |arxiv=astro-ph/0401513
 |bibcode=2006NewAR..50..436C
 |citeseerx=10.1.1.316.4895
 |doi=10.1016/j.newar.2006.02.035
 |access-date=25 October 2017
|archive-date=22 September 2017
|archive-url=https://web.archive.org/web/20170922220807/http://www.phyast.pitt.edu/%7Ewmwv/Papers/Wood-Vasey_SNfactory.pdf
 |url-status=live
 }}</ref>

As survey programmes rapidly increase the number of detected supernovae, collated collections of observations (light decay curves, astrometry, pre-supernova observations, spectroscopy) have been assembled. The Pantheon data set, assembled in 2018, detailed 1048 supernovae.<ref> {{Cite journal
 |last1=Scolnic |first1=D. M. 
 |last2=Jones |first2=D. O. 
 |last3=Rest |first3=A.
 |date=2018
 |title=The Complete Light-curve Sample of Spectroscopically Confirmed SNe Ia from Pan-STARRS1 and Cosmological Constraints from the Combined Pantheon Sample
 |journal=[[The Astrophysical Journal]]
 |volume=859 |issue=2 
 |page=101
 |doi=10.3847/1538-4357/aab9bb
 |arxiv=1710.00845 
 |bibcode=2018ApJ...859..101S 
 |s2cid=54676349 
 |doi-access=free 
 }}</ref> In 2021, this data set was expanded to 1701 light curves for 1550 supernovae taken from 18 different surveys, a 50% increase in under 3 years.<ref> {{Cite journal
 |last1=Scolnic |first1=D. M. 
 |last2=Brout |first2=D.
 |last3=Carr |first3=A. 
 |date=2021
 |title=The Pantheon+ Analysis: The Full Dataset and Light-Curve Release
 |journal=[[Astrophysical Journal Letters]]
 |volume=938 |issue=2 
 |page=113
 |arxiv=2112.03863
 |doi=10.3847/1538-4357/ac8b7a |bibcode=2022ApJ...938..113S
 |s2cid=246652657 
 |doi-access=free 
 }}</ref>