Editing Synchrotron radiation (section)

==In astronomy==
[[Image:M87 jet.jpg|thumb|225px|[[Messier 87]]'s [[astrophysical jet]], [[Hubble Space Telescope|HST]] image. The blue light from the jet emerging from the bright [[active galactic nucleus|AGN]] core, towards the lower right, is due to synchrotron radiation.]]
Synchrotron radiation is also generated by astronomical objects, typically where relativistic electrons spiral (and hence change velocity) through magnetic fields.
Two of its characteristics include [[power-law]] energy spectra and polarization.<ref>Vladimir A. Bordovitsyn, "[https://books.google.com/books?id=rG9ZWoCtwagC&dq=%22Synchrotron++radiation%22+astronomy&pg=PA385 Synchrotron Radiation in Astrophysics]" (1999) ''[http://www.worldscibooks.com/physics/3492.html Synchrotron Radiation Theory and Its Development]'', {{ISBN|981-02-3156-3}}</ref> It is considered to be one of the most powerful tools in the study of extra-solar magnetic fields wherever relativistic charged particles are present. Most known cosmic radio sources emit synchrotron radiation. It is often used to estimate the strength of large cosmic magnetic fields as well as analyze the contents of the interstellar and intergalactic media.<ref name="Klein 2014">{{cite book|last=Klein|first=Ulrich|title=Galactic and intergalactic magnetic fields|publisher=Springer|location=Cham, Switzerland & New York|year=2014|isbn=978-3-319-08942-3|oclc=894893367}}</ref>

===History of detection===
This type of radiation was first detected in the [[Crab Nebula]] in 1956 by [[Jan Hendrik Oort]] and [[Theodore Walraven]],<ref>{{cite journal|last=Oort|first=J. H.|title=Polarization and composition of the Crab nebula|journal=Bulletin of the Astronomical Institutes of the Netherlands|volume=12|page=285|year=1956|bibcode=1956BAN....12..285O}}</ref> and a few months later in a jet emitted by [[Messier 87]] by [[Geoffrey Burbidge|Geoffrey R. Burbidge]].<ref>{{cite journal|last=Burbidge|first=G. R.|title=On Synchrotron Radiation from Messier 87|journal=The Astrophysical Journal|publisher=IOP Publishing|volume=124|year=1956|issn=0004-637X|doi=10.1086/146237|page=416|bibcode=1956ApJ...124..416B|doi-access=free}}</ref> It was confirmation of a prediction by [[Iosif Samuilovich Shklovsky|Iosif S. Shklovsky]] in 1953. However, it had been predicted earlier (1950) by [[Hannes Alfvén]] and Nicolai Herlofson.<ref>{{cite journal|last1=Alfvén|first1=H.|last2=Herlofson|first2=N.|title=Cosmic Radiation and Radio Stars|journal=Physical Review|publisher=APS|volume=78|issue=5|date=1 June 1950|issn=0031-899X|doi=10.1103/physrev.78.616|page=616|bibcode=1950PhRv...78..616A}}</ref> [[Solar flares]] accelerate particles that emit in this way, as suggested by R. Giovanelli in 1948 and described by J.H. Piddington in 1952.<ref>{{cite journal|last=Piddington|first=J. H.|title=Thermal Theories of the High-Intensity Components of Solar Radio-Frequency Radiation|journal=Proceedings of the Physical Society. Section B|publisher=IOP Publishing|volume=66|issue=2|year=1953|issn=0370-1301|doi=10.1088/0370-1301/66/2/305|pages=97–104|bibcode=1953PPSB...66...97P}}</ref>

T. K. Breus noted that questions of priority on the history of astrophysical synchrotron radiation are complicated, writing:
{{blockquote|In particular, the Russian physicist [[Vitaly Ginzburg|V.L. Ginzburg]] broke his relationships with [[Iosif Samuilovich Shklovsky|I.S. Shklovsky]] and did not speak with him for 18 years. In the West, [[Thomas Gold]] and Sir [[Fred Hoyle]] were in dispute with [[Hannes Alfvén|H. Alfven]] and N. Herlofson, while K.O. Kiepenheuer and G. Hutchinson were ignored by them.{{clarify|reason=Ignored by the first pair, the second pair, or all four? As I see things, Wikipedia editors don't get to simply wrap quotation marks around an interesting nugget of source material and then pass the muddiness through with no guidance to the casual reader provided.|date=October 2022}}<ref>Breus, T. K., "[http://adsabs.harvard.edu/abs/2001IAIss..26...88B Istoriya prioritetov sinkhrotronnoj kontseptsii v astronomii %t] (Historical problems of the priority questions of the synchrotron concept in astrophysics)" (2001) in ''Istoriko-Astronomicheskie Issledovaniya'', Vyp. 26, pp. 88–97, 262 (2001)</ref>}}

[[Image:Crab Nebula.jpg|225px|thumb|The bluish glow from the central region of the [[Crab Nebula]] is due to synchrotron radiation.]]

=== From supermassive black holes ===

It has been suggested that [[supermassive black hole]]s produce synchrotron radiation in "jets", generated by the gravitational acceleration of ions in their polar magnetic fields. The nearest such observed jet is from the core of the galaxy [[Messier 87]].  This jet is interesting for producing the illusion of [[superluminal]] motion as observed from the frame of Earth. This phenomenon is caused because the jets are traveling very near the speed of light ''and'' at a very small angle towards the observer. Because at every point of their path the high-velocity jets are emitting light, the light they emit does not approach the observer much more quickly than the jet itself. Light emitted over hundreds of years of travel thus arrives at the observer over a much smaller time period, giving the illusion of faster than light travel, despite the fact that there is actually no violation of [[special relativity]].<ref>{{cite web|last=Chase|first=Scott I.|title=Apparent Superluminal Velocity of Galaxies|url=http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/Superluminal/superluminal.html|access-date=22 August 2012}}</ref>

===Pulsar wind nebulae===
A class of [[Astronomical object|astronomical source]]s where synchrotron emission is important is [[pulsar wind nebula]]e, also known as [[plerion]]s, of which the [[Crab nebula]] and its associated [[pulsar]] are archetypal.
Pulsed emission gamma-ray radiation from the Crab has recently been observed up to ≥25&nbsp;GeV,<ref>{{cite journal|last1=Aliu|first1=E.|last2=Anderhub|first2=H.|last3=Antonelli|first3=L. A.|last4=Antoranz|first4=P.|last5=Backes|first5=M.|last6=Baixeras|first6=C.|last7=Barrio|first7=J. A.|last8=Bartko|first8=H.|last9=Bastieri|first9=D.|last10=Becker|first10=J. K.|display-authors=5|title=Observation of Pulsed γ-Rays Above 25 GeV from the Crab Pulsar with MAGIC|journal=Science|volume=322|issue=5905|date=21 November 2008|issn=0036-8075|doi=10.1126/science.1164718|pages=1221–1224|pmid=18927358|arxiv=0809.2998|bibcode=2008Sci...322.1221A|s2cid=5387958 }}</ref> probably due to synchrotron emission by electrons trapped in the strong magnetic field around the pulsar.
Polarization in the Crab nebula<ref>{{cite journal|last1=Dean|first1=A. J.|last2=Clark|first2=D. J.|last3=Stephen|first3=J. B.|last4=McBride|first4=V. A.|last5=Bassani|first5=L.|last6=Bazzano|first6=A.|last7=Bird|first7=A. J.|last8=Hill|first8=A. B.|last9=Shaw|first9=S. E.|last10=Ubertini|first10=P.|display-authors=5|title=Polarized Gamma-Ray Emission from the Crab|journal=Science|publisher=American Association for the Advancement of Science (AAAS)|volume=321|issue=5893|date=29 August 2008|issn=0036-8075|doi=10.1126/science.1149056|pages=1183–1185|pmid=18755970 |bibcode=2008Sci...321.1183D|s2cid=206509342}}</ref> at energies from 0.1 to 1.0 MeV, illustrates this typical property of synchrotron radiation.

===Interstellar and intergalactic media===
Much of what is known about the magnetic environment of the [[interstellar medium]] and [[intergalactic medium]] is derived from observations of synchrotron radiation. Cosmic ray electrons moving through the medium interact with relativistic plasma and emit synchrotron radiation which is detected on Earth. The properties of the radiation allow astronomers to make inferences about the magnetic field strength and orientation in these regions. However, accurate calculations of field strength cannot be made without knowing the relativistic electron density.<ref name="Klein 2014"/>

===In supernovae===
When a star explodes in a supernova, the fastest ejecta move at semi-relativistic speeds approximately 10% the [[speed of light]].<ref>{{cite journal |last1=Soderberg |first1=A. |author1-link= Alicia M. Soderberg |last2=Chevalier |first2=R. A. |last3=Kulkarni |first3=S. R. |last4=Frail |first4=D. A. |date=November 2006 |title=The Radio and X-Ray Luminous SN 2003bg and the Circumstellar Density Variations around Radio Supernovae |journal=The Astrophysical Journal |volume=651 |issue=2 |pages=1005–1018 |doi=10.1086/507571|doi-access=free |arxiv=astro-ph/0512413 |bibcode=2006ApJ...651.1005S }}</ref> This blast wave gyrates electrons in ambient magnetic fields and generates synchrotron emission, revealing the radius of the blast wave at the location of the emission.<ref>{{cite journal |last1=Chevalier |first1=R. A. |date=May 1998 |title=Synchrotron Self-Absorption in Radio Supernovae |journal=The Astrophysical Journal |volume=499 |issue=2 |pages=810–819 |doi=10.1086/305676|doi-access=free |bibcode=1998ApJ...499..810C }}</ref> Synchrotron emission can also reveal the strength of the magnetic field at the front of the shock wave, as well as the circumstellar density it encounters, but strongly depends on the choice of energy partition between the magnetic field, proton kinetic energy, and electron kinetic energy. Radio synchrotron emission has allowed astronomers to shed light on mass loss and stellar winds that occur just prior to stellar death.<ref>{{cite journal |last1=Margutti |first1=Raffaella |last2=Kamble |first2=A. |last3=Milisavljevic |first3=D. |last4=Zapartas |first4=E. |last5=de Mink |first5=S. E. |last6=Drout |first6=M. |last7=Chornock |first7=R. |display-authors=1 |date=February 2017 |title=Ejection of the Massive Hydrogen-rich Envelope Timed with the Collapse of the Stripped SN 2014C |journal=The Astrophysical Journal |volume=835 |issue=2 |page=140 |doi=10.3847/1538-4357/835/2/140|hdl=10150/624387 |hdl-access=free |doi-access=free |pmid=28684881 |pmc=5495200 |arxiv=1601.06806 |bibcode=2017ApJ...835..140M }}</ref><ref>{{cite journal |last1=DeMarchi |first1=Lindsay |last2=Margutti |first2=R. |last3=Dittman |first3=J. |last4=Brunthaler |first4=A. |display-authors=1 |date=October 2022 |title=Radio Analysis of SN2004C Reveals an Unusual CSM Density Profile as a Harbinger of Core Collapse |journal=The Astrophysical Journal |volume=938 |issue=1 |page=84 |doi=10.3847/1538-4357/ac8c26|doi-access=free |arxiv=2203.07388 |bibcode=2022ApJ...938...84D }}</ref>