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Supernova remnant
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<h2 id="stages">Stages</h2> <p>An SNR passes through the following stages as it expands:<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> </p> <ol><li>Free expansion of the ejecta, until they sweep up their own weight in circumstellar or <a href="/facts/Interstellar_medium/mokU0WEz">interstellar medium</a>. This can last tens to a few hundred years depending on the density of the surrounding gas.</li> <li>Sweeping up of a shell of shocked circumstellar and interstellar gas. This begins the Sedov-Taylor phase, which can be well modeled by a self-similar analytic solution (see <a href="/facts/Blast_wave/aDgFJWLm">blast wave</a>). Strong <a href="/facts/X-ray/wseP79cN">X-ray</a> emission traces the strong shock waves and hot shocked gas.</li> <li>Cooling of the shell, to form a thin (< 1 <a href="/facts/Parsec/SwSsk57J">pc</a>), dense (1 to 100 million atoms per cubic metre) shell surrounding the hot (few million kelvin) interior. This is the pressure-driven snowplow phase. The shell can be clearly seen in optical emission from recombining ionized <a href="/facts/Hydrogen/BoYHjl0J">hydrogen</a> and ionized <a href="/facts/Oxygen/acyn6o8r">oxygen</a> atoms.</li> <li>Cooling of the interior. The dense shell continues to expand from its own momentum. This stage is best seen in the radio emission from neutral hydrogen atoms.</li> <li>Merging with the surrounding interstellar medium. When the supernova remnant slows to the speed of the random velocities in the surrounding medium, after roughly 30,000 years, it will merge into the general turbulent flow, contributing its remaining kinetic energy to the turbulence.</li></ol> Supernova remnant ejecta producing <a href="/facts/Nebular_hypothesis/IT3D6MpE">planet-forming material</a> <h2 id="types-of-supernova-remnant">Types of supernova remnant</h2> <p>There are three types of supernova remnant: </p> <ul><li>Shell-like, such as <a href="/facts/Cassiopeia_A/wqKS2fqb">Cassiopeia A</a></li> <li>Composite, in which a shell contains a central <a href="/facts/Pulsar_wind_nebula/zRtFJJGt">pulsar wind nebula</a>, such as G11.2-0.3 or G21.5-0.9.</li> <li>Mixed-morphology (also called "thermal composite") remnants, in which central thermal X-ray emission is seen, enclosed by a radio shell. The thermal X-rays are primarily from swept-up interstellar material, rather than supernova ejecta. Examples of this class include the SNRs W28 and W44. (Confusingly, W44 additionally contains a <a href="/facts/Pulsar/f8c7S5LQ">pulsar</a> and pulsar wind nebula; so it is simultaneously both a "classic" composite and a thermal composite.)</li></ul> Supernova remnantsHBH 3 (<a href="/facts/Spitzer_Space_Telescope/Ic1xXIYb">Spitzer Space Telescope</a>; August 2, 2018)G54.1+0.3 (November 16, 2018) <p>Remnants which could only be created by significantly higher ejection energies than a standard supernova are called <i>hypernova remnants</i>, after the high-energy <a href="/facts/Hypernova/7f0l3sQB">hypernova</a> explosion that is assumed to have created them.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> </p> <h2 id="origin-of-cosmic-rays">Origin of cosmic rays</h2> <p>Supernova remnants are considered the major source of <a href="/facts/Galactic_cosmic_ray/uxCVdTKd">galactic cosmic rays</a>.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a><a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a><a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> The connection between cosmic rays and supernovas was first suggested by <a href="/facts/Walter_Baade/olu54Cof">Walter Baade</a> and <a href="/facts/Fritz_Zwicky/E4S5dcmD">Fritz Zwicky</a> in 1934. <a href="/facts/Vitaly_Ginzburg/uscYaLgY">Vitaly Ginzburg</a> and Sergei Syrovatskii in 1964 remarked that if the efficiency of cosmic ray acceleration in supernova remnants is about 10 percent, the cosmic ray losses of the Milky Way are compensated. This hypothesis is supported by a specific mechanism called "shock wave acceleration" based on <a href="/facts/Enrico_Fermi/cmYcY15H">Enrico Fermi</a>'s ideas, which is still under development.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p><p>In 1949, Fermi proposed a model for the acceleration of cosmic rays through particle collisions with magnetic clouds in the <a href="/facts/Interstellar_medium/mokU0WEz">interstellar medium</a>.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> This process, known as the "Second Order <a href="/facts/Fermi_acceleration/3MRG8YvV">Fermi Mechanism</a>", increases particle energy during head-on collisions, resulting in a steady gain in energy. A later model to produce Fermi Acceleration was generated by a powerful shock front moving through space. Particles that repeatedly cross the front of the shock can gain significant increases in energy. This became known as the "First Order Fermi Mechanism".<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> </p><p>Supernova remnants can provide the energetic shock fronts required to generate ultra-high energy cosmic rays. Observation of the <a href="/facts/SN_1006/jus9wu5p">SN 1006</a> remnant in the X-ray has shown <a href="/facts/Synchrotron_emission/mTsSKmRz">synchrotron emission</a> consistent with it being a source of cosmic rays.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> However, for energies higher than about 1018 eV a different mechanism is required as supernova remnants cannot provide sufficient energy.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p><p>It is still unclear whether supernova remnants accelerate cosmic rays up to PeV energies. The future telescope <a href="/facts/Cherenkov_Telescope_Array/q6QmtgFG">CTA</a> will help to answer this question. </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/List_of_supernova_remnants/GGrMzCx1">List of supernova remnants</a></li> <li><a href="/facts/Local_Bubble/aMb38wle">Local Bubble</a></li> <li><a href="/facts/Nova_remnant/zlVAtW7X">Nova remnant</a></li> <li><a href="/facts/Planetary_nebula/5Vy84cPq">Planetary nebula</a></li> <li><a href="/facts/Sigma-D_relation/5RtAueNI">Sigma-D relation</a></li> <li><a href="/facts/Superbubble/9TzmFEYd">Superbubble</a></li></ul> <h2 id="external-links">External links</h2> Wikimedia Commons has media related to Supernova remnants. <ul><li><a href="https://sne.space/?event=snr">List of All Known Galactic and Extragalactic Supernovae</a> on the Open Supernova Catalog (these are not supernova remnants yet)</li> <li><a href="http://www.mrao.cam.ac.uk/surveys/snrs/">Galactic SNR Catalogue</a> (D. A. Green, University of Cambridge)</li> <li>Chandra observations of supernova remnants: <a href="http://hea-www.cfa.harvard.edu/ChandraSNR/">catalog</a>, <a href="http://chandra.harvard.edu/photo/category/snr.html">photo album</a>, <a href="https://web.archive.org/web/20020918225120/http://www.astro.psu.edu/users/green/Main/main5.html">selected picks</a></li> <li><a href="http://www.ipac.caltech.edu/2mass/gallery/images_snrs.html">2MASS images of Supernova Remnants</a></li> <li><a href="https://agile.gsfc.nasa.gov/docs/objects/snrs/snrstext.html">NASA: Introduction to Supernova Remnants</a> <a href="https://web.archive.org/web/20070311020249/http://agile.gsfc.nasa.gov/docs/objects/snrs/snrstext.html">Archived</a> 2007-03-11 at the <a href="/facts/Wayback_Machine/nmQ3a6JC">Wayback Machine</a></li> <li><a href="https://imagine.gsfc.nasa.gov/docs/science/know_l2/supernova_remnants.html">NASA's Imagine: Supernova Remnants</a></li> <li><a href="http://www.universetoday.com/am/publish/afterlife_supernova.html">Afterlife of a Supernova</a> on UniverseToday.com</li> <li><a href="http://xstructure.inr.ac.ru/x-bin/theme3.py?level=2&index1=59244">Supernova remnant</a> on arxiv.org</li> <li><a href="http://messier.seds.org/snr.html">Supernova Remnants</a>, SEDS</li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Discovery of most recent supernova in our galaxy May 14, 2008 <a href="http://chandra.harvard.edu/press/08_releases/press_051408.html" target="_blank">http://chandra.harvard.edu/press/08_releases/press_051408.html</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Reynolds, Stephen P. (2008). "Supernova Remnants at High Energy". Annual Review of Astronomy and Astrophysics. 46 (46): 89–126. Bibcode:2008ARA&A..46...89R. doi:10.1146/annurev.astro.46.060407.145237. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Lai, Shih-Ping; Chu, You-Hua; Chen, C.-H. Rosie; Ciardullo, Robin; Grebel, Eva K. (2001). "A Critical Examination of Hypernova Remnant Candidates in M101. I. MF 83". The Astrophysical Journal. 547 (2): 754–764. arXiv:astro-ph/0009238. Bibcode:2001ApJ...547..754L. doi:10.1086/318420. S2CID 14620463. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>K. Koyama; R. Petre; E.V. Gotthelf; U. Hwang; et al. (1995). "Evidence for shock acceleration of high-energy electrons in the supernova remnant SN1006". Nature. 378 (6554): 255–258. Bibcode:1995Natur.378..255K. doi:10.1038/378255a0. S2CID 4257238. <a href="https://zenodo.org/record/1233170" target="_blank">https://zenodo.org/record/1233170</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>"Supernova produces cosmic rays". BBC News. November 4, 2004. Retrieved 2006-11-28. <a href="http://news.bbc.co.uk/2/hi/science/nature/3981619.stm" target="_blank">http://news.bbc.co.uk/2/hi/science/nature/3981619.stm</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>"SNR and Cosmic Ray Acceleration". NASA Goddard Space Flight Center. Archived from the original on 1999-02-21. Retrieved 2007-02-08. <a href="https://web.archive.org/web/19990221015927/http://imagine.gsfc.nasa.gov/docs/features/topics/snr_group/cosmic_rays.html" target="_blank">https://web.archive.org/web/19990221015927/http://imagine.gsfc.nasa.gov/docs/features/topics/snr_group/cosmic_rays.html</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>S.P. Reynolds (2011). "Particle acceleration in supernova-remnant shocks". Astrophysics and Space Science. 336 (1): 257–262. arXiv:1012.1306. Bibcode:2011Ap&SS.336..257R. doi:10.1007/s10509-010-0559-8. S2CID 118735190. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>E. Fermi (1949). "On the Origin of the Cosmic Radiation". Physical Review. 75 (8): 1169–1174. Bibcode:1949PhRv...75.1169F. doi:10.1103/PhysRev.75.1169. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>"Ultra-High Energy Cosmic Rays". University of Utah. Retrieved 2006-08-10. <a href="http://www.cosmic-ray.org/reading/uhecr.html" target="_blank">http://www.cosmic-ray.org/reading/uhecr.html</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>K. Koyama; R. Petre; E.V. Gotthelf; U. Hwang; et al. (1995). "Evidence for shock acceleration of high-energy electrons in the supernova remnant SN1006". Nature. 378 (6554): 255–258. Bibcode:1995Natur.378..255K. doi:10.1038/378255a0. S2CID 4257238. <a href="https://zenodo.org/record/1233170" target="_blank">https://zenodo.org/record/1233170</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>"Ultra-High Energy Cosmic Rays". University of Utah. Retrieved 2006-08-10. <a href="http://www.cosmic-ray.org/reading/uhecr.html" target="_blank">http://www.cosmic-ray.org/reading/uhecr.html</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> </ol>