Oh-My-God particle

It is not known what kind of particle it was, but most cosmic rays are protons. If $m\_\backslash mathrm\{p\}$ is the rest mass of the particle and $E\_\backslash mathrm\{K\}$ is its kinetic energy (energy above the rest mass energy), then its speed was very close to $\backslash sqrt\{1-[m\_\backslash mathrm\{p\}c^2/(E\_\backslash mathrm\{K\}+m\_\backslash mathrm\{p\}c^2)]^2\}$ times the speed of light. Since $E\_\backslash mathrm\{K\}\; \backslash gg\; m\_\backslash mathrm\{p\}c^2$, this ratio can be simplified to $1-\backslash frac\{1\}\{2\}[m\_\backslash mathrm\{p\}c^2/E\_\backslash mathrm\{K\}]^2$. Assuming it was a proton, for which $m\_\backslash mathrm\{p\}c^2$ is 938 MeV, this means it was traveling at {{val|0.9999999999999999999999957}} times the speed of light, its Lorentz factor was {{val|3.2|e=11}} and its rapidity was {{val|27.1}}. This is 1.3 femtometers per second less than the speed of light, so if a photon were traveling alongside the proton, it would take over 245,000 years for the photon to gain a 1 cm lead, as seen from the Earth's reference frame. Due to special relativity, the relativistic time dilation experienced by a proton traveling at this speed would be extreme. If the proton originated from a distance of 1.5 billion light years, it would take approximately 1.71 days in the reference frame of the proton to travel that distance.

The energy of the particle was some 40 million times that of the highest-energy protons that have been produced in any terrestrial particle accelerator. However, only a small fraction of this energy was available for its interaction with a nucleus in the Earth's atmosphere, with most of the energy remaining in the form of kinetic energy of the center of mass of the products of the interaction. If $m\_\backslash mathrm\{t\}$ is the mass of the "target" nucleus, the energy available for such a collision is{{cite book |url=https://books.google.com/books?id=JW0gBAAAQBAJ&pg=PA1 |title=Accelerator Physics at the Tevatron Collider |vauthors=Holmes S, Moore R, Peoples J, Shiltsev V |date=29 May 2014 |publisher=Springer |isbn=9781493908851 |veditors=Lebedev V, Shiltsev V |series=Particle Acceleration and Detection |page=1 |chapter=Chapter 1. Introduction |doi=10.1007/978-1-4939-0885-1 |access-date=6 February 2024 |via=Google Books}}

$$\backslash sqrt\{\; 2E\_\backslash mathrm\{K\}m\_\backslash mathrm\{t\}c^2+(m\_\backslash mathrm\{p\}+m\_\backslash mathrm\{t\})^2c^4\; \}-(m\_\backslash mathrm\{p\}+m\_\backslash mathrm\{t\})c^2$$

which for large $E\_\backslash mathrm\{K\}$ is approximately

$$\backslash sqrt\{\; 2E\_\backslash mathrm\{K\}m\_\backslash mathrm\{t\}c^2\}.$$

For the Oh-My-God particle hitting a nitrogen nucleus, this gives 2900 TeV, which is roughly 200 times higher than the highest collision energy of the Large Hadron Collider, in which two high-energy particles going opposite directions collide.{{cite news |author=Jowett, John |date=November 2015 |title=Lead-ion collisions: The LHC achieves a new energy record |website=CERN Bulletin |url=https://cds.cern.ch/journal/CERNBulletin/2015/49/News%20Articles/2105084?ln=en |access-date=February 24, 2016 |archive-date=August 26, 2023 |archive-url=https://web.archive.org/web/20230826152920/https://cds.cern.ch/journal/CERNBulletin/2015/49/News%20Articles/2105084?ln=en |url-status=live }}{{cite news |author=Nerlich, Steve |date=13 June 2011 |title=Oh-My-God particles |website=Universe Today |via=phys.org |url=https://phys.org/news/2011-06-oh-my-god-particles.html |access-date=June 30, 2019 |archive-date=June 30, 2019 |archive-url=https://web.archive.org/web/20190630191829/https://phys.org/news/2011-06-oh-my-god-particles.html |url-status=live }} In the center-of-mass frame of reference (which was moving, in our frame of reference, at almost the speed of light), the products of the collision would therefore have had around 2900 TeV of energy. This would have transformed the nucleus into many particles moving apart at almost light speed in the center-of-mass frame of reference. As with other cosmic rays, the collision generated a cascade of relativistic particles as the particles interacted with other nuclei.

{{original research section|date=April 2023}}

The Oh-My-God particle{{'}}s energy was estimated as {{val|3.2|0.9|e=20|ul=eV}}, or {{val|51|14|ul=J}}. Although this amount is phenomenally large for a single elementary particle – far outstripping the highest energy that human technology can generate in a particle – it is still far below the level of the Planck scale, where exotic physics is expected. Though a subatomic particle, its energy was comparable to the gravitational potential energy of a 1 kilogram object that could fall 5 meters off a two-story building.

The Oh-My-God particle had {{10^|20}} (100 quintillion) times the photon energy of visible light, equivalent to a {{convert|5|oz|order=flip|adj=on|sp=us}} baseball travelling at about {{convert|28|m/s|km/h mph|abbr=on}}. {{Sky|5|40|48|+|48|0|0|98000000}} Its energy was 20 million times greater than the highest photon energy measured in electromagnetic radiation emitted by an extragalactic object, the blazar Markarian 501.{{cite journal |author1=Aharonian, F. |collaboration=The HEGRA Collaboration |year=1999 |title=The time averaged TeV energy spectrum of Mkn 501 of the extraordinary 1997 outburst as measured with the stereoscopic Cherenkov telescope system of HEGRA |journal=Astronomy & Astrophysics |volume=349 |pages=11–28 |arxiv=astro-ph/9903386v2 |bibcode=1999A&A...349...11A |s2cid=15448541 |url=https://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1999A%26A...349...11A&defaultprint=YES&filetype=.pdf |access-date=June 19, 2023 |archive-date=June 19, 2023 |archive-url=https://web.archive.org/web/20230619200950/https://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1999A%26A...349...11A&defaultprint=YES&filetype=.pdf |url-status=live }}{{update-inline|date=February 2022}}

It had a relativistic mass equivalent to around {{val|3.4|e=11}} daltons, or {{val|2.4|e=10}} nitrogen nuclei.

While the particle's energy was higher than anything achieved in terrestrial accelerators, it was still about 40 million times lower than the Planck energy ({{val|1.2208901|e=28|u=eV}}). Particles of that energy would be required in order to expose effects on the Planck scale. A proton with that much energy would travel {{val|1.665|e=15}} times closer to the speed of light than the Oh-My-God particle did. As viewed from Earth and observed in Earth's reference frame, it would take about {{val|3.579|e=20|u=years}} ({{val|2.59|e=10}} times the current age of the universe) for a photon to overtake a Planck energy proton with a 1 cm lead.{{citation needed |date=March 2020}}

Since the first observation, hundreds of similar events (energy {{val|5.7|e=19|u=eV}} or greater) have been recorded, confirming the phenomenon.{{Cite journal |last1=Abdul Halim |first1=A. |last2=Abreu |first2=P. |last3=Aglietta |first3=M. |last4=Allekotte |first4=I. |last5=Allison |first5=P. |last6=Almeida Cheminant |first6=K. |last7=Almela |first7=A. |last8=Alvarez-Muñiz |first8=J. |last9=Ammerman Yebra |first9=J. |last10=Anastasi |first10=G. A. |last11=Anchordoqui |first11=L. |last12=Andrada |first12=B. |last13=Andringa |first13=S. |last14=Aramo |first14=C. |last15=Araújo Ferreira |first15=P. R. |date=2023-02-01 |title=A Catalog of the Highest-energy Cosmic Rays Recorded during Phase I of Operation of the Pierre Auger Observatory |journal=The Astrophysical Journal Supplement Series |volume=264 |issue=2 |pages=50 |doi=10.3847/1538-4365/aca537 |bibcode=2023ApJS..264...50A |s2cid=254070054 |issn=0067-0049 |doi-access=free |hdl=2133/25771 |hdl-access=free }}{{cite journal | last1 = Abbasi | first1 = R. U. | last2 = Abe | first2 = M. | last3 = Abu-Zayyad | first3 = T. | last4 = Allen | first4 = M. | last5 = Anderson | first5 = R. | last6 = Azuma | first6 = R. | last7 = Barcikowski | first7 = E. | last8 = Belz | first8 = J. W. | last9 = Bergman | first9 = D. R. | last10 = Blake | first10 = S. A. | last11 = Cady | first11 = R. | last12 = Chae | first12 = M. J. | last13 = Cheon | first13 = B. G. | last14 = Chiba | first14 = J. | last15 = Chikawa | first15 = M. | last16 = Cho | first16 = W. R. | last17 = Fujii | first17 = T. | last18 = Fukushima | first18 = M. | last19 = Goto | first19 = T. | last20 = Hanlon | first20 = W. | last21 = Hayashi | first21 = Y. | last22 = Hayashida | first22 = N. | last23 = Hibino | first23 = K. | last24 = Honda | first24 = K. | last25 = Ikeda | first25 = D. | last26 = Inoue | first26 = N. | last27 = Ishii | first27 = T. | last28 = Ishimori | first28 = R. | last29 = Ito | first29 = H. | last30 = Ivanov | first30 = D. | last31 = Jui | first31 = C. C. H. | last32 = Kadota | first32 = K. | last33 = Kakimoto | first33 = F. | last34 = Kalashev | first34 = O. | last35 = Kasahara | first35 = K. | last36 = Kawai | first36 = H. | last37 = Kawakami | first37 = S. | last38 = Kawana | first38 = S. | last39 = Kawata | first39 = K. | last40 = Kido | first40 = E. | last41 = Kim | first41 = H. B. | last42 = Kim | first42 = J. H. | last43 = Kim | first43 = J. H. | last44 = Kitamura | first44 = S. | last45 = Kitamura | first45 = Y. | last46 = Kuzmin | first46 = V. | last47 = Kwon | first47 = Y. J. | last48 = Lan | first48 = J. | last49 = Lim | first49 = S. I. | last50 = Lundquist | first50 = J. P. | last51 = Machida | first51 = K. | last52 = Martens | first52 = K. | last53 = Matsuda | first53 = T. | last54 = Matsuyama | first54 = T. | last55 = Matthews | first55 = J. N. | last56 = Minamino | first56 = M. | last57 = Mukai | first57 = K. | last58 = Myers | first58 = I. | last59 = Nagasawa | first59 = K. | last60 = Nagataki | first60 = S. | last61 = Nakamura | first61 = T. | last62 = Nonaka | first62 = T. | last63 = Nozato | first63 = A. | last64 = Ogio | first64 = S. | last65 = Ogura | first65 = J. | last66 = Ohnishi | first66 = M. | last67 = Ohoka | first67 = H. | last68 = Oki | first68 = K. | last69 = Okuda | first69 = T. | last70 = Ono | first70 = M. | last71 = Oshima | first71 = A. | last72 = Ozawa | first72 = S. | last73 = Park | first73 = I. H. | last74 = Pshirkov | first74 = M. S. | last75 = Rodriguez | first75 = D. C. | last76 = Rubtsov | first76 = G. | last77 = Ryu | first77 = D. | last78 = Sagawa | first78 = H. | last79 = Sakurai | first79 = N. | last80 = Sampson | first80 = A. L. | last81 = Scott | first81 = L. M. | last82 = Shah | first82 = P. D. | last83 = Shibata | first83 = F. | last84 = Shibata | first84 = T. | last85 = Shimodaira | first85 = H. | last86 = Shin | first86 = B. K. | last87 = Smith | first87 = J. D. | last88 = Sokolsky | first88 = P. | last89 = Springer | first89 = R. W. | last90 = Stokes | first90 = B. T. | last91 = Stratton | first91 = S. R. | last92 = Stroman | first92 = T. A. | last93 = Suzawa | first93 = T. | last94 = Takamura | first94 = M. | last95 = Takeda | first95 = M. | last96 = Takeishi | first96 = R. | last97 = Taketa | first97 = A. | last98 = Takita | first98 = M. | last99 = Tameda | first99 = Y. | last100 = Tanaka | first100 = H. | last101 = Tanaka | first101 = K. | last102 = Tanaka | first102 = M. | last103 = Thomas | first103 = S. B. | last104 = Thomson | first104 = G. B. | last105 = Tinyakov | first105 = P. | last106 = Tkachev | first106 = I. | last107 = Tokuno | first107 = H. | last108 = Tomida | first108 = T. | last109 = Troitsky | first109 = S. | last110 = Tsunesada | first110 = Y. | last111 = Tsutsumi | first111 = K. | last112 = Uchihori | first112 = Y. | last113 = Udo | first113 = S. | last114 = Urban | first114 = F. | last115 = Vasiloff | first115 = G. | last116 = Wong | first116 = T. | last117 = Yamane | first117 = R. | last118 = Yamaoka | first118 = H. | last119 = Yamazaki | first119 = K. | last120 = Yang | first120 = J. | last121 = Yashiro | first121 = K. | last122 = Yoneda | first122 = Y. | last123 = Yoshida | first123 = S. | last124 = Yoshii | first124 = H. | last125 = Zollinger | first125 = R. | last126 = Zundel | first126 = Z. | display-authors = 5 |title=Indications of intermediate-scale anisotropy of cosmic rays with energy greater than 57 EeV in the northern sky, measured with the surface detector of the Telescope Array Experiment |journal=The Astrophysical Journal |date=2014-07-14 |volume=790 |issue=2 |page=L21 |doi=10.1088/2041-8205/790/2/L21 |arxiv=1404.5890 |bibcode=2014ApJ...790L..21A|s2cid=118481211 | issn = 0004-637X | eissn = 1538-4357 }} These ultra-high-energy cosmic ray particles are very rare; the energy of most cosmic ray particles is between {{10^|7}} eV and {{10^|10}} eV.

More recent studies using the Telescope Array Project have suggested a source of the particles within a 20 degree radius "warm spot" in the direction of the constellation Ursa Major.{{cite journal |last1=Wolchover |first1=Natalie |author-link=Natalie Wolchover |date=May 14, 2015 |title=The particle that broke a cosmic speed limit |url=https://www.quantamagazine.org/the-particle-that-broke-a-cosmic-speed-limit-20150514/ |url-status=live |journal=Quanta Magazine |issn=2640-2661 |archive-url=https://web.archive.org/web/20230708064650/https://www.quantamagazine.org/the-particle-that-broke-a-cosmic-speed-limit-20150514/ |archive-date=July 8, 2023 |access-date=February 6, 2024 |df=dmy-all}}{{cite journal |url=https://www.science.org/content/article/physicists-spot-potential-source-oh-my-god-particles |title=Physicists spot potential source of 'Oh-My-God' particles |journal=Science |date=2014-07-08 |first=Adrian |last=Cho |doi=10.1126/article.22871 |doi-broken-date=November 1, 2024 |issn=0036-8075 |eissn=1095-9203 |df=dmy-all |access-date=June 30, 2022 |archive-date=April 12, 2022 |archive-url=https://web.archive.org/web/20220412155837/https://www.science.org/content/article/physicists-spot-potential-source-oh-my-god-particles |url-status=live }}

The Amaterasu particle, named after the sun goddess in Japanese mythology, was detected in 2021 and later identified in 2023, using the Telescope Array observatory in Utah, United States. It had an energy exceeding 240 exa-electron volts ({{val|2.4|e=20}} eV).{{Cite journal |last=Conover |first=Emily |date=January 13, 2024 |title=A high-energy cosmic ray hails from the void |url=https://www.sciencenews.org/article/rare-energetic-cosmic-ray-mysterious-origins |journal=Science News |pages=5}} This particle appears to have emerged from the Local Void, an empty area of space bordering the Milky Way galaxy.{{cite journal |last1=Devlin |first1=Hannah |date=2023-11-24 |title='What the heck is going on?' Extremely high-energy particle detected falling to Earth. |url=https://www.theguardian.com/science/2023/nov/24/amaterasu-extremely-high-energy-particle-detected-falling-to-earth |url-status=live |journal=The Guardian |archive-url=https://web.archive.org/web/20231124093358/https://www.theguardian.com/science/2023/nov/24/amaterasu-extremely-high-energy-particle-detected-falling-to-earth |archive-date=November 24, 2023 |access-date=February 6, 2024}} It contained an amount of energy comparable to dropping a brick from the height of the waist. No promising astronomical object matching the direction from which the cosmic ray arrived has been identified.{{cite journal|first1=|last1=|title=Second OMG cosmic ray particle breaks physics again|journal=Cosmosmagazine.com|url=https://cosmosmagazine.com/space/astrophysics/second-largest-cosmic-ray-particle/#:~:text=The%20ultra%20high-energy%20cosmic%20ray%20was%20named%20%E2%80%9CAmaterasu%2C%E2%80%9D,in%20a%20paper%20published%20in%20the%20journal%20Science.|date=2023-11-24|access-date=November 24, 2023|archive-date=November 24, 2023|archive-url=https://web.archive.org/web/20231124121233/https://cosmosmagazine.com/space/astrophysics/second-largest-cosmic-ray-particle/#:~:text=The%20ultra%20high-energy%20cosmic%20ray%20was%20named%20%E2%80%9CAmaterasu%2C%E2%80%9D,in%20a%20paper%20published%20in%20the%20journal%20Science.|url-status=live}}

• {{annotated link|Greisen–Zatsepin–Kuzmin limit}}
• {{annotated link|HZE ion}}
• {{annotated link|Solar energetic particles}}
• Amaterasu particle (2021) – 240 Eev

{{reflist |25em}}

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