Editing Supernova (section)

===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
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 |arxiv=0803.1487
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 }}</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
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 |year=1969
 |title=Early Supernova Luminosity
 |journal=[[The Astrophysical Journal]]
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 |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>
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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
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 |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.
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 |book-title=Small Telescope Astronomy on Global Scale
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 |publisher=[[Astronomical Society of the Pacific]]
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 |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">
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 |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
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 |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>
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 |journal=Revista Mexicana de Fisica
 |volume=45 |issue=2 |pages=36
 |arxiv=hep-ph/9901300
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}}</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>
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 |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
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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>
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 |arxiv=astro-ph/0208138
 |bibcode=2003PhRvD..67h1303L
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 }}</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>
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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>