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Evidence record

Where do cosmic rays come from?

Every sentence on the exploration belongs to at least one claim below. Each says what kind of statement it is, what it rests on, what the evidence does not establish, and how far it was checked. Nothing here is a score, and none of it is a verdict on a belief or a theory.

Last checked 24 September 2026.

  • Source checked: 51
  • Presented as open: 2
  • A judgement, not a fact: 8

If something here is wrong, misquoted, out of date or unfair, write to support@unknownoceans.com and give the claim number, which does not change.

What the question takes for granted

An origin question about the highest-energy particles in nature. The ordinary cosmic rays are thought to be galactic; the page is about the extreme ones, whose sources lie outside the galaxy and within the local universe and have not been identified.

  • Cosmic rays come from somewhere that could in principle be identified

    Established

    The arrival directions are anisotropic and the energy losses limit the distance, so the sources are real objects in a bounded volume. The obstacle is deflection, not absence.

  • There is one kind of source for all of them

    Open

    The page treats the ordinary and the extreme cosmic rays separately, and the candidate list for the extreme ones has several classes. Nothing establishes that one class makes them all.

  • The particles are ordinary nuclei

    Contested

    Measurements point to a mix that grows heavier with energy; the Telescope Array keeps open an unknown particle, and Unger and Farrar read the 2021 event as iron.

How the question is labelled

Claim: The most energetic particles

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

Energy per particle, not speed. The highest energies were measured for a handful of events, each with an uncertainty of tens of per cent.

Later work looked for

Particle Data Group review, revised October 2025: cosmic rays remain the highest-energy particles observed; nothing changes it.

Corrected

24 September 2026. Previously: “The fastest things” The sources describe these particles by their energy, not their speed, and light itself is faster than any particle with mass. The title now says what the sources say.

Claim 1 · checked 24 September 2026 · AI-assisted audit

Claim: Cosmic rays

Kind
Framing. Signposting. It asserts nothing a source could check.

The question

Claim: One particle can carry fifty joules

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

One event, measured at 320 plus or minus 90 exa-electronvolts; the joule figure carries the same uncertainty.

Later work looked for

Crossref, 2023 on, "extremely energetic cosmic ray": the 2021 Telescope Array event, about 40 joules, is the largest since; the 1991 figure still stands as the record.

Claim 3 · checked 24 September 2026 · AI-assisted audit

Claim: and nobody can point at what threw it

Kind
Open question. Something the page says is not known.
Review
Presented as open. The page says this is unresolved, and the review found that it is.

  • Supports

    An extremely energetic cosmic ray observed by a surface detector arrayPossible sources of the cosmic ray

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: Even taking into account the range of possible GMF deflections and primary mass, we do not identify any candidate sources for this event.

  • Supports

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.2.2, arrival directions

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: it remains challenging to definitively ascertain the origin of UHECRs, primarily due to their deviation caused by the insufficiently constrained galactic and extragalactic magnetic fields

What this does not establish

Candidate source classes exist, and a later analysis proposes one for the 2021 event (claim 68); no individual source has been identified.

Claim 4 · checked 24 September 2026 · AI-assisted audit

Claim: Charged particles from space hit the atmosphere constantly

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Observation of a large-scale anisotropy in the arrival directions of cosmic rays above 8 x 10^18 eVintroduction, first paragraph

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: Particles with energies ranging from below 10⁹ eV up to beyond 10²⁰ eV, known as cosmic rays, constantly hit the Earth’s atmosphere.

    Notation restored: Superscripts restored from the arXiv LaTeX source of 1709.07321v1, read 2026-09-24. The text as extracted reads: Particles with energies ranging from below 10 9 eV up to beyond 10 20 eV , known as cosmic rays, constantly hit the Earth’s atmosphere.

Later work looked for

Particle Data Group review, 2025: the intensity above 1 GeV is about ten thousand per square metre per second per steradian; nothing changes it.

Claim 5 · checked 24 September 2026 · AI-assisted audit

Claim: and a rare few carry energies no accelerator on Earth can approach

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    An extremely energetic cosmic ray observed by a surface detector arrayintroduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: energies greater than 10¹⁸ eV (1 exa-electron volt, EeV), about a million times higher than reached by human-made accelerators

    Notation restored: Superscript restored from the sentence itself, which glosses the figure as 1 exa-electron volt; an exa-electronvolt is 10¹⁸ eV by definition. Not checked against a rendered copy. The text as extracted reads: energies greater than 1018 eV (1 exa-electron volt, EeV), about a million times higher than reached by human-made accelerators

What this does not establish

The comparison is of the particle’s energy in the ground’s frame. In a collision with the air the centre-of-mass energy is far lower, about 700 TeV for the 2021 event, which is still beyond any accelerator.

Later work looked for

Crossref, 2023 on, "ultra-high-energy cosmic rays": no accelerator has come near; nothing changes it.

Claim 6 · checked 24 September 2026 · AI-assisted audit

Claim: Their paths are bent by magnetic fields on the way

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.2.2, experimental results

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: since CRs are charged they are deflected by the galactic and intergalactic magnetic fields

Later work looked for

Particle Data Group review, 2025: unchanged.

Claim 7 · checked 24 September 2026 · AI-assisted audit

Claim: so the sky they arrive from is not the sky they came from

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    An extremely energetic cosmic ray observed by a surface detector arrayintroduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: so their arrival directions do not necessarily point to their sources

  • Supports

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.2.2, arrival directions

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: it remains challenging to definitively ascertain the origin of UHECRs, primarily due to their deviation caused by the insufficiently constrained galactic and extragalactic magnetic fields

  • Supports

    Observation of a large-scale anisotropy in the arrival directions of cosmic rays above 8 x 10^18 eVintroduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: Magnetic fields are not well constrained by data, but if we adopt recent models of the Galactic magnetic field [7,8], typical values of the deflections of particles crossing the Galaxy are a few tens of degrees forE/Z = 10 EeV

  • Qualifies

    An extremely energetic cosmic ray observed by a surface detector arrayintroduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: UHECRs with energies above the GZK cutoff are expected to be deflected less strongly by magnetic fields due to their high kinetic energies

What this does not establish

How far the sky is shifted depends on charge and energy: a few tens of degrees at 10 exa-electronvolts per unit charge, less for a proton at the extreme end.

Later work looked for

Particle Data Group review, 2025: the fields remain insufficiently constrained; nothing changes it.

Claim 8 · checked 24 September 2026 · AI-assisted audit

Claim: A cosmic ray is not a ray.

Kind
About a word. What a word in the original language means, or how it is translated.
Review
Source checked. The cited passage was read, and it says this.

Claim 9 · checked 24 September 2026 · AI-assisted audit

Claim: It is a single atomic nucleus, usually a proton, moving close to the speed of light.

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.1

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: Charged CRs are composed mostly of protons, helium, and other nuclei, as well as electrons, positrons and anti-protons.

  • Supports

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.2.1

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: Protons are dominating the CR flux by number and by energy below∼10TeV

  • Supports

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.1

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: relativistic nuclei suffer little energy losses

  • Qualifies

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.2.2, composition

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: Above that energy, the data from the largest statistical sample of events collected with the FD of the Pierre Auger Observatory indicate that the composition is mixed with the mean mass steadily growing.

What this does not establish

A small share of cosmic rays are electrons, positrons and antiprotons. "Usually a proton" holds for the flux as a whole; above a few exa-electronvolts the measured mix grows heavier.

Later work looked for

Particle Data Group review, revised October 2025: protons dominate below about 10 TeV; above about 2 EeV the mix grows heavier. Page unchanged on this point.

Corrected

24 September 2026. Previously: “It is a single atomic nucleus, usually a proton, moving so close to the speed of light that its collision with the upper atmosphere produces a shower of secondary particles kilometres across.” Showers kilometres across come only from the highest-energy particles (Auger gives about 20 square kilometres at 10 exa-electronvolts); most cosmic rays make nothing of the kind. The sentence is split and the shower confined to the highest energies.

Claim 10 · checked 24 September 2026 · AI-assisted audit

Claim: At the highest energies its collision with the upper atmosphere produces a shower of secondary particles kilometres across.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

How the method works; not a finding later work revises.

Claim 11 · checked 24 September 2026 · AI-assisted audit

Claim: The ordinary ones most likely come from within our own galaxy, though even their sources have not been pinned down.

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.2.2, astrophysical interpretation

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: Cosmic rays below ≃ 10 PeV most likely have a galactic origin.

    Notation restored: Spacing restored from the review’s PDF (1 December 2025) rendered with pdftotext -layout, read 2026-09-24. The text as extracted reads: Cosmic rays below ≃10PeV most likely have a galactic origin.

  • Supports

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.1

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: yet the dominant source of locally measured CRs have not been unambiguously identified

  • Supports

    The astrophysics of ultrahigh-energy cosmic raysintroduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: The dominant component of cosmic rays observed on Earth originate in the Galaxy.

  • Context

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.1

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: In the Galaxy, the prime candidates are supernova remnants

What this does not establish

"Ordinary" here means below about 10 peta-electronvolts. Supernova remnants are the leading candidates, not an established answer.

Later work looked for

Particle Data Group review, revised October 2025: supernova remnants remain the prime galactic candidates, alongside star cluster winds, binaries and microquasars, and the dominant source is still not identified. Page corrected.

Corrected

24 September 2026. Previously: “The ordinary ones are understood.” Overstated. The Particle Data Group review (2025) says the dominant source of locally measured cosmic rays has not been unambiguously identified, and that those below about 10 PeV most likely have a galactic origin.

Claim 12 · checked 24 September 2026 · AI-assisted audit

Claim: The rare, extreme ones are a problem that has been open for more than sixty years.

Kind
Historical claim. A statement about the past that historical evidence can test.
Review
Source checked. The cited passage was read, and it says this.

Counted from Linsley’s report of a particle above 100 exa-electronvolts in 1963.

  • Supports

    In search of a source for the 320 EeV Fly’s Eye cosmic raysection 1

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field

    The source reads: Discovering the origins of the highest energy cosmic rays has been a goal in astroparticle physics for three decades since the first reported detection of a particle with energy greater than 100 EeV (10^20 eV) (Linsley 1963).

    From Linsley’s 1963 detection to 2026 is 63 years; the 2025 Particle Data Group review still calls the sources open.

  • Supports

    Observation of a large-scale anisotropy in the arrival directions of cosmic rays above 8 x 10^18 eVintroduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: The existence of cosmic rays with such ultra-high energies has been known for more than 50 years [1, 2], but the sites and mechanisms of their production remain a mystery.

  • Supports

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.2.2

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: the nature and identity of their sources as well as the acceleration mechanisms that boost the particles to these extreme energies remain open questions

Claim 13 · checked 24 September 2026 · AI-assisted audit

What arrives

Claim: What arrives

Kind
Framing. Signposting. It asserts nothing a source could check.

The extreme end is absurd

Claim: The extreme end is absurd

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

A figure of speech for the energies in claims 16 to 21, which the sources describe as far beyond any accelerator.

Claim 15 · checked 24 September 2026 · AI-assisted audit

Claim: In 1991 a detector in Utah recorded a single particle with an energy of about 3 times 10 to the 20 electronvolts, or 51 joules.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

320 plus or minus 93 exa-electronvolts, systematic and statistical uncertainties combined. The kind of particle was not determined.

Later work looked for

Crossref, 2023 on, "Fly's Eye" and "extremely energetic cosmic ray": the Telescope Array (2023) still lists the 1991 event, at 320 EeV, as the highest reported; nothing changes it.

Corrected

24 September 2026. Previously: “In 1991 a detector in Utah recorded a particle with an energy of about 3 times 10 to the 20 electronvolts, which is a single subatomic nucleus carrying roughly the kinetic energy of a thrown baseball.” Bird and others say the shower "does not uniquely identify the type of primary particle", so "nucleus" said more than the paper; and no cited source makes the baseball comparison. The paper’s own figure, 51 joules, replaces it.

Claim 16 · checked 24 September 2026 · AI-assisted audit

Claim: It was not a fluke of one instrument.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    An extremely energetic cosmic ray observed by a surface detector arrayComparison with previous events

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: Previously reported extremely high-energy cosmic ray events include a 320 EeV particle in 1991 ( 26), a 213 EeV particle in 1993 ( 27) and a 280 EeV particle in 2001 ( 28).

What this does not establish

All of these events were recorded in the northern hemisphere (claim 19).

Later work looked for

Crossref, 2023 on: the 2021 event is the latest; nothing changes it.

Claim 17 · checked 24 September 2026 · AI-assisted audit

Claim: In 2021 the Telescope Array recorded another, of 244 exa-electronvolts, and reported it in 2023.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    An extremely energetic cosmic ray observed by a surface detector arrayEnergetic particle on 27 May 2021; Table 1

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: the event on 27 May 2021 has a reconstructed energy of 244 ± 29 (stat.) ⁺⁵¹₋₇₆ (syst.) EeV

    Notation restored: Superscripts, subscript and spacing restored from the arXiv LaTeX source of 2311.14231v1, read 2026-09-24. The text as extracted reads: the event on 27 May 2021 has a reconstructed energy of 244± 29 (stat.) +51 −76 (syst.) EeV

  • Qualifies

    Where did the Amaterasu particle come from?section 6

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Model

    The source reads: we considered two energies for the particle: the nominal energy of Enom = (2.12

What this does not establish

244 plus or minus 29 (statistical), plus 51 or minus 76 (systematic). Unger and Farrar, reading it as a heavy nucleus, use about 212 or 164.

Later work looked for

Crossref, 2024 on, "Amaterasu": Unger and Farrar (2024) assign about 212 or 164 EeV if the particle is an iron nucleus; recorded in limits.

Claim 18 · checked 24 September 2026 · AI-assisted audit

Claim: A 2022 search of the Pierre Auger Observatory’s data, in Argentina, found nothing above 166, though the two experiments’ energy scales differ.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

Reported here as the Telescope Array paper reports it; the 2022 Auger search itself was not read. The two energy scales differ, so the numbers are not directly comparable.

Later work looked for

Crossref, 2022 on, "Pierre Auger" "highest energy events": no later Auger event above 166 EeV found in what was read.

Corrected

24 September 2026. Previously: “” Added. The two largest detectors disagree at the top of the spectrum, and the Telescope Array paper says so itself.

Claim 19 · checked 24 September 2026 · AI-assisted audit

Claim: Arrivals at these energies are extraordinarily rare, and the exposures say how rare: Auger collected thirty thousand particles above 8 exa-electronvolts from 76,800 square kilometre steradian years of watching, and above 100 exa-electronvolts the flux is under one particle per square kilometre per century.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Observation of a large-scale anisotropy in the arrival directions of cosmic rays above 8 x 10^18 eVabstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: Using 3×10⁴ cosmic rays above 8×10¹⁸ electron volts, recorded with the Pierre Auger Observatory from a total exposure of 76,800 square kilometers steradian year

    Notation restored: Superscripts restored from the arXiv LaTeX source of 1709.07321v1, read 2026-09-24. The text as extracted reads: Using 3×104 cosmic rays above 8×1018 electron volts, recorded with the Pierre Auger Observatory from a total exposure of 76,800 square kilometers steradian year

  • Supports

    An extremely energetic cosmic ray observed by a surface detector arrayThe Telescope Array experiment

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: At energies greater than 100 EeV , the flux of cosmic rays is less than one particle per century per square kilometer

Later work looked for

Particle Data Group review, 2025: under one particle per square kilometre per year above 30 EeV, consistent; nothing changes it.

Corrected

24 September 2026. Previously: “the Pierre Auger Observatory collected” The observatory is now named in the sentence before.

Claim 20 · checked 24 September 2026 · AI-assisted audit

Claim: That is why the detectors cover hundreds or thousands of square kilometres.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

Particle Data Group review, 2025: Auger about 3,000 and the Telescope Array about 700 square kilometres; nothing changes it.

Corrected

24 September 2026. Previously: “That is why the detectors are the size of cities or larger.” No cited source makes the comparison with cities. The papers give the areas: 700 square kilometres for the Telescope Array, 3,000 for Auger.

Claim 21 · checked 24 September 2026 · AI-assisted audit

Claim: Scale

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: 10^20 eV

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Detection of a cosmic ray with measured energy well beyond the expected spectral cutoff due to cosmic microwave radiationabstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: We report the detection of a 51-joule ... cosmic ray by the Fly's Eye air shower detector in Utah.

  • Supports

    An extremely energetic cosmic ray observed by a surface detector arrayEnergetic particle on 27 May 2021

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: the event on 27 May 2021 has a reconstructed energy of 244 ± 29 (stat.) ⁺⁵¹₋₇₆ (syst.) EeV

    Notation restored: Superscripts, subscript and spacing restored from the arXiv LaTeX source of 2311.14231v1, read 2026-09-24. The text as extracted reads: the event on 27 May 2021 has a reconstructed energy of 244± 29 (stat.) +51 −76 (syst.) EeV

What this does not establish

An order of magnitude: the two largest events measured 320 and 244 exa-electronvolts, that is 3.2 and 2.44 times 10^20 eV.

Later work looked for

Crossref, 2023 on: the record stands; nothing changes it.

Claim 23 · checked 24 September 2026 · AI-assisted audit

Claim: Highest recorded energies

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

Crossref, 2023 on: nothing higher reported.

Claim 24 · checked 24 September 2026 · AI-assisted audit

Claim: About forty million times the energy the Large Hadron Collider gives a proton.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    An extremely energetic cosmic ray observed by a surface detector arrayEnergetic particle on 27 May 2021

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: This energy is ∼4×10⁷ times higher than the ∼7 tera-electron volts (TeV) protons accelerated by the Large Hadron Collider (LHC)

    Notation restored: Superscripts, subscript and spacing restored from the arXiv LaTeX source of 2311.14231v1, read 2026-09-24. The text as extracted reads: This energy is∼ 4×107 times higher than the∼7 tera-electron volts (TeV) protons accelerated by the Large Hadron Collider (LHC)

What this does not establish

The Telescope Array’s comparison for its 2021 event. For the 1991 event the ratio is somewhat larger.

Later work looked for

The comparison is the Telescope Array’s own, for its 244 EeV event; the LHC beam energy has not changed its order since; nothing changes it.

Claim 25 · checked 24 September 2026 · AI-assisted audit

Claim: 1 per km² per year

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Observation of a large-scale anisotropy in the arrival directions of cosmic rays above 8 x 10^18 eVintroduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: for energies above 10 EeV (1 EeV ≡ 10¹⁸ eV), the flux is about one particle per km² per year

    Notation restored: Superscripts restored from the arXiv LaTeX source of 1709.07321v1, read 2026-09-24. The text as extracted reads: for energies above 10 EeV (1 EeV≡ 1018 eV), the flux is about one particle per km2 per year

What this does not establish

Auger gives it as "about one".

Later work looked for

Particle Data Group review, 2025: under one per square kilometre per year above 30 EeV, consistent; nothing changes it.

Claim 26 · checked 24 September 2026 · AI-assisted audit

Claim: Arrival rate above 10^19 eV

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Observation of a large-scale anisotropy in the arrival directions of cosmic rays above 8 x 10^18 eVintroduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: for energies above 10 EeV (1 EeV ≡ 10¹⁸ eV), the flux is about one particle per km² per year

    Notation restored: Superscripts restored from the arXiv LaTeX source of 1709.07321v1, read 2026-09-24. The text as extracted reads: for energies above 10 EeV (1 EeV≡ 1018 eV), the flux is about one particle per km2 per year

Later work looked for

Particle Data Group review, 2025: consistent; nothing changes it.

Claim 27 · checked 24 September 2026 · AI-assisted audit

Claim: Rarer still above that.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    An extremely energetic cosmic ray observed by a surface detector arrayThe Telescope Array experiment

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: At energies greater than 100 EeV , the flux of cosmic rays is less than one particle per century per square kilometer

Later work looked for

Particle Data Group review, 2025: the flux falls steeply above a few tens of EeV; nothing changes it.

Corrected

24 September 2026. Previously: “Rarer still above that. The reason ground arrays cover thousands of square kilometres.” The second sentence repeated the passage, and "thousands" is true of Auger but not of the Telescope Array, at 700.

Claim 28 · checked 24 September 2026 · AI-assisted audit

Claim: ~100 Mpc

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    The astrophysics of ultrahigh-energy cosmic rayssection 2.2

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Above GZK energies, observable sources must lie within about 100 Mpc, the so-called GZK horizon or GZK sphere

  • Supports

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.1

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: For protons above 10 EeV, photo-pion production limits the propagation distances to ∼ 100 Mpc

    Notation restored: Spacing restored from the review’s PDF (1 December 2025) rendered with pdftotext -layout, read 2026-09-24. The text as extracted reads: For protons above10EeV, photo-pion production limits the propagation distances to∼100Mpc

  • Qualifies

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.2.2, arrival directions

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: This imposes a horizon to possible sources of ∼ 250 Mpc for protons and Fe nuclei, but shorter for nuclei in between these two, for instance ∼ 5 Mpc for He and ∼ 100 Mpc for Si at energies above ≃ 50 EeV

    Notation restored: Spacing restored from the review’s PDF (1 December 2025) rendered with pdftotext -layout, read 2026-09-24. The text as extracted reads: This imposes a horizon to possible sources of∼250Mpc for protons and Fe nuclei, but shorter for nuclei in between these two, for instance∼5Mpc for He and∼100Mpc for Si at energies above≃50EeV

What this does not establish

An order of magnitude. Estimates depend on the energy, the kind of nucleus and how the horizon is defined: the Particle Data Group review gives about 100 Mpc in one place and about 250 Mpc for protons and iron above 50 EeV in another.

Later work looked for

Particle Data Group review, 2025: about 100 Mpc for protons above 10 EeV, but a horizon of about 250 Mpc for protons and iron above 50 EeV in another estimate; recorded in limits.

Claim 29 · checked 24 September 2026 · AI-assisted audit

Claim: How far such a particle can travel

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    The astrophysics of ultrahigh-energy cosmic rayssection 2.2

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: protons and iron nuclei may reach us from sources at distances up to about 100 Mpc

What this does not establish

For standard particles above the threshold energy. A particle immune to these collisions would travel further; none is known.

Later work looked for

Particle Data Group review, 2025: see claim 29.

Claim 30 · checked 24 September 2026 · AI-assisted audit

Claim: Beyond that it loses energy to collisions with the microwave background.

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

Nuclei also break apart on the infrared background, not only the microwave one.

Later work looked for

How the method works; not a finding later work revises.

Claim 31 · checked 24 September 2026 · AI-assisted audit

They come from outside the galaxy

Claim: They come from outside the galaxy

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.2.2, astrophysical interpretation

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: The observed dipolar anisotropy in arrival directions imply that above8EeV they have their origin in extragalactic sources.

What this does not establish

Above about 8 exa-electronvolts. Below a few exa-electronvolts most cosmic rays are thought to be galactic.

Later work looked for

Particle Data Group review, revised October 2025: the dipole is now at 6.8 standard deviations; the conclusion is unchanged.

Claim 32 · checked 24 September 2026 · AI-assisted audit

Claim: Above about 8 times 10 to the 18 electronvolts, the arrival directions are not uniform.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

Particle Data Group review, 2025: the Auger dipole has grown to 6.8 standard deviations, and Telescope Array data combined with Auger’s agree; page updated in claim 35.

Claim 33 · checked 24 September 2026 · AI-assisted audit

Claim: The Pierre Auger Observatory, reporting on thirty thousand events in 2017, found a dipole of about 6.5 per cent: a slight excess from one half of the sky, its axis some 125 degrees from the centre of our own galaxy.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

Amplitude 6.5 per cent, plus 1.3 or minus 0.9.

Later work looked for

Particle Data Group review, 2025: later Auger data give 7.4 per cent at about 113 degrees; the 2017 figures are reported as 2017 figures and the update added (claim 35).

Claim 34 · checked 24 September 2026 · AI-assisted audit

Claim: With more data it now stands at about 7.4 per cent and 6.8 standard deviations, about 113 degrees from the galactic centre.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.2.2, arrival directions

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: The Pierre Auger Collaboration has discovered a large-scale dipolar anisotropy at energies above ... 8 EeV with 6.8σ significance ... The amplitude of the dipolar anisotropy is d = 0.074 ... the dipole points at a direction that is ∼ 113° away from the Galactic Center

    Notation restored: Spacing restored from the review’s PDF (1 December 2025) rendered with pdftotext -layout, read 2026-09-24. The text as extracted reads: The Pierre Auger Collaboration has discovered a large-scale dipolar anisotropy at energies above ... 8EeV with6.8σsignificance ... The amplitude of the dipolar anisotropy isd = 0.074 ... the dipole points at a direction that is∼113◦away from the Galactic Center

What this does not establish

Taken from the Particle Data Group review; the Auger paper behind the update was not read here.

Later work looked for

Particle Data Group review, revised October 2025, is the newer work; page updated.

Corrected

24 September 2026. Previously: “” Added. The 2017 figures have been superseded by later Auger data, as the Particle Data Group review (2025) reports.

Claim 35 · checked 24 September 2026 · AI-assisted audit

Claim: That is the cleanest evidence that the particles above this energy are made outside our galaxy.

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

"Cleanest" is the page’s judgement; both sources treat the dipole as the evidence for an extragalactic origin.

Later work looked for

Particle Data Group review, 2025: unchanged.

Corrected

24 September 2026. Previously: “That is the cleanest evidence that the highest-energy particles are not produced locally.” The dipole is measured above 8 exa-electronvolts, not only at the highest energies, and "locally" was vague. The claim now says what Auger and the Particle Data Group say.

Claim 36 · checked 24 September 2026 · AI-assisted audit

Claim: A galactic population would be expected to be brightest towards the galactic centre, and it is not.

Kind
What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

An expectation, as Auger words it ("might be expected"), which depends on how galactic sources and fields are modelled.

Later work looked for

How the method works; not a finding later work revises.

Corrected

24 September 2026. Previously: “A galactic population would be brightest towards the galactic centre, and it is not.” Auger states this as an expectation, not a certainty.

Claim 37 · checked 24 September 2026 · AI-assisted audit

And they cannot come from very far away either

Claim: And they cannot come from very far away either

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    The astrophysics of ultrahigh-energy cosmic rayssection 2.2

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Above GZK energies, observable sources must lie within about 100 Mpc, the so-called GZK horizon or GZK sphere

What this does not establish

Holds for protons and nuclei above the threshold. The Telescope Array paper notes that an unknown kind of particle immune to these collisions could come from further away.

Later work looked for

Particle Data Group review, 2025: the horizon stands, at 100 to 250 Mpc depending on the estimate.

Claim 38 · checked 24 September 2026 · AI-assisted audit

Claim: A proton above a certain energy collides with photons of the microwave background and loses energy in the process.

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

How the method works; not a finding later work revises.

Claim 39 · checked 24 September 2026 · AI-assisted audit

Claim: The effect puts a horizon on the highest-energy particles: above the threshold the sources have to lie within about a hundred megaparsecs, and for a particle as energetic as the 1991 one within about thirty.

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    The astrophysics of ultrahigh-energy cosmic rayssection 2.2

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Above GZK energies, observable sources must lie within about 100 Mpc, the so-called GZK horizon or GZK sphere

  • Supports

    Detection of a cosmic ray with measured energy well beyond the expected spectral cutoff due to cosmic microwave radiationsection 1

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Model

    The source reads: For protons above 300 EeV, the attenuation length is less than 30 Mpc (Stecker, 1968). ... The source of this particle should be sought within about 30 Mpc.

  • Supports

    An extremely energetic cosmic ray observed by a surface detector arrayPossible sources of the cosmic ray

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Model

    The source reads: the average propagation distance at an energy of 244 EeV is calculated to be ∼ 30 Mpc for both proton and iron primaries

  • Qualifies

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.2.2, arrival directions

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: This imposes a horizon to possible sources of ∼ 250 Mpc for protons and Fe nuclei, but shorter for nuclei in between these two, for instance ∼ 5 Mpc for He and ∼ 100 Mpc for Si at energies above ≃ 50 EeV

    Notation restored: Spacing restored from the review’s PDF (1 December 2025) rendered with pdftotext -layout, read 2026-09-24. The text as extracted reads: This imposes a horizon to possible sources of∼250Mpc for protons and Fe nuclei, but shorter for nuclei in between these two, for instance∼5Mpc for He and∼100Mpc for Si at energies above≃50EeV

What this does not establish

The hundred-megaparsec figure is an order of magnitude that depends on energy, nucleus and definition; the Particle Data Group review also gives about 250 Mpc for protons and iron above 50 EeV.

Later work looked for

Particle Data Group review, 2025: one estimate puts the horizon at about 250 Mpc for protons and iron above 50 EeV; recorded in limits. Unger and Farrar (2024) put the 2021 event’s source within 8 to 50 Mpc; consistent.

Claim 40 · checked 24 September 2026 · AI-assisted audit

Claim: In cosmological terms that is the neighbourhood.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from claim 40; the Telescope Array paper speaks of "the local extragalactic neighborhood".

Claim 41 · checked 24 September 2026 · AI-assisted audit

Claim: So the source is outside the galaxy and inside the local universe, which is a small enough volume to contain a catalogue of candidates and a large enough one to contain a great many of them.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Combines claim 36 (above 8 exa-electronvolts) with claim 40 (above the threshold energy). The two apply to overlapping but not identical energies, and the argument holds for the highest-energy particles.

Claim 42 · checked 24 September 2026 · AI-assisted audit

What might be throwing them

Claim: What might be throwing them

Kind
Framing. Signposting. It asserts nothing a source could check.

What accelerates them

Claim: What accelerates them

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: Most astrophysical objects cannot hold a particle long enough to accelerate it this far.

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

The test is the Hillas criterion: a source must be large enough and magnetised enough to keep the particle inside it while it gains energy.

  • Supports

    The astrophysics of ultrahigh-energy cosmic rayssection 5, Hillas criterion

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Requiring that candidate sources be capable of confining particles up to Emax, translates into a simple selection criterium for candidate sources with magnetic field strength B and extension R (Hillas 1984)

  • Supports

    The astrophysics of ultrahigh-energy cosmic rayssection 5, Hillas criterion

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Most astrophysical objects do not even reach the iron confinement line up to 10²⁰ eV, leaving the best candidates for UHECR acceleration to be: neutron stars, Active Galactic Nuclei (AGN), Gamma Ray Bursts (GRBs), and accretion shocks in the intergalactic medium.

    Notation restored: Superscript restored from the arXiv LaTeX source of 1101.4256v1, read 2026-09-24. The text as extracted reads: Most astrophysical objects do not even reach the iron confinement line up to 10 20 eV, leaving the best candidates for UHECR acceleration to be: neutron stars, Active Galactic Nuclei (AGN), Gamma Ray Bursts (GRBs), and accretion shocks in the intergalactic medium.

Later work looked for

Particle Data Group review, 2025: the Hillas criterion is still the fundamental constraint; nothing changes it.

Claim 45 · checked 24 September 2026 · AI-assisted audit

Claim: What survives that test is a short list: neutron stars, the jets of active galaxies, gamma-ray bursts, and accretion shocks in the intergalactic medium and in galaxy clusters.

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    The astrophysics of ultrahigh-energy cosmic rayssection 5, Hillas criterion

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Most astrophysical objects do not even reach the iron confinement line up to 10²⁰ eV, leaving the best candidates for UHECR acceleration to be: neutron stars, Active Galactic Nuclei (AGN), Gamma Ray Bursts (GRBs), and accretion shocks in the intergalactic medium.

    Notation restored: Superscript restored from the arXiv LaTeX source of 1101.4256v1, read 2026-09-24. The text as extracted reads: Most astrophysical objects do not even reach the iron confinement line up to 10 20 eV, leaving the best candidates for UHECR acceleration to be: neutron stars, Active Galactic Nuclei (AGN), Gamma Ray Bursts (GRBs), and accretion shocks in the intergalactic medium.

  • Supports

    The astrophysics of ultrahigh-energy cosmic rayssection 5

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Popular shock regions for UHECR acceleration are GRB shocks, jets and hot spots of AGN, and gravitational accretion shocks.

  • Supports

    An extremely energetic cosmic ray observed by a surface detector arrayintroduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: or large-scale accretion shocks around clusters of galaxies

  • Qualifies

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.1

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: The candidate sources for extra-galactic CRs are Active Galactic Nuclei (AGN) [52], specifically blazars and radio galaxies, gamma-ray bursts [53], starburst galaxies [54,55], pulsars [56] and magnetars [57].

What this does not establish

The list is Kotera and Olinto’s (2011). The Particle Data Group’s current list also includes starburst galaxies. Passing the test is necessary, not sufficient.

Later work looked for

Particle Data Group review, 2025: the current list adds starburst galaxies and names pulsars and magnetars; recorded in limits.

Claim 46 · checked 24 September 2026 · AI-assisted audit

Claim: Each can be made to work on paper.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Kotera and Olinto review acceleration models for each candidate and call the size-and-field test necessary but not sufficient.

Claim 47 · checked 24 September 2026 · AI-assisted audit

Claim: None has been tied to a specific event at the highest energies

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.2.2, arrival directions

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: it remains challenging to definitively ascertain the origin of UHECRs, primarily due to their deviation caused by the insufficiently constrained galactic and extragalactic magnetic fields

  • Supports

    An extremely energetic cosmic ray observed by a surface detector arraySummary and conclusions

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: The arrival direction of this event does not align with any known astronomical objects thought to be a potential source of UHECRs, even after taking into account deflection by the GMF under various assumptions.

Later work looked for

Crossref, 2023 on, "ultra-high-energy cosmic ray sources": statistical hints only; the page now reports the strongest (claim 50).

Claim 48 · checked 24 September 2026 · AI-assisted audit

Claim: and the absence of clear sources in those arrival directions is itself one of the puzzles

Kind
Open question. Something the page says is not known.
Review
Presented as open. The page says this is unresolved, and the review found that it is.

  • Supports

    An extremely energetic cosmic ray observed by a surface detector arrayDistribution of other TA events

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: The lack of a nearby source for the 244 EeV event could be due to larger magnetic deflections than predicted by the GMF models caused by a heavy primary particle or stronger magnetic fields than in the models.

  • Supports

    In search of a source for the 320 EeV Fly’s Eye cosmic rayabstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Observational study: associations, not causes

    The source reads: Our search finds no likely source within 50 Mpc in the direction from which the particle arrived.

Claim 49 · checked 24 September 2026 · AI-assisted audit

Claim: The strongest hints so far are statistical: in Auger’s data, an excess of arrivals above 38 exa-electronvolts across a wide region around the radio galaxy Centaurus A, at four standard deviations.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.2.2, arrival directions

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: With data from the Pierre Auger Observatory, a 4σ excess of events above 38 EeV was found in a region of angular radius ≃ 27° centered on the radio galaxy Centaurus A (CenA)

    Notation restored: Spacing restored from the review’s PDF (1 December 2025) rendered with pdftotext -layout, read 2026-09-24. The text as extracted reads: With data from the Pierre Auger Observatory, a4σexcess of events above 38EeV was found in a region of angular radius≃27◦centered on the radio galaxy Centaurus A (CenA)

  • Context

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.2.2, arrival directions

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: The Telescope Array Collaboration has also reported an excess of events with energies above 57 EeV (the so-called hot spot) in the northern sky in the direction of R.A. = 144.0°, Dec. = 40.5°, with a 2.8σ significance

    Notation restored: Spacing restored from the review’s PDF (1 December 2025) rendered with pdftotext -layout, read 2026-09-24. The text as extracted reads: The Telescope Array Collaboration has also reported an excess of events with energies above57EeV (the so-calledhot spot) in the northern sky in the direction of R.A.= 144.0◦, Dec. = 40.5◦, with a 2.8σsignificance

What this does not establish

The region is about 27 degrees in radius, so the excess does not single out Centaurus A itself. The Auger paper behind it was not read here. A weaker correlation with nearby starburst galaxies (3.8 standard deviations) and a Telescope Array hot spot in the north (2.8) are the other hints.

Later work looked for

Particle Data Group review, revised October 2025, is the newer work; page updated.

Corrected

24 September 2026. Previously: “” Added. "None has been tied" is true, but the page gave no sign of the statistical associations the field reports; the Particle Data Group review (2025) lists them.

Claim 50 · checked 24 September 2026 · AI-assisted audit

The problem with pointing

Claim: The problem with pointing

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: A charged particle is deflected by every magnetic field it passes through, including our own galaxy’s, and those fields are only roughly mapped.

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.2.2

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: since CRs are charged they are deflected by the galactic and intergalactic magnetic fields

  • Supports

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.2.2, arrival directions

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: it remains challenging to definitively ascertain the origin of UHECRs, primarily due to their deviation caused by the insufficiently constrained galactic and extragalactic magnetic fields

  • Supports

    Observation of a large-scale anisotropy in the arrival directions of cosmic rays above 8 x 10^18 eVintroduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: Magnetic fields are not well constrained by data, but if we adopt recent models of the Galactic magnetic field [7,8], typical values of the deflections of particles crossing the Galaxy are a few tens of degrees forE/Z = 10 EeV

Later work looked for

Particle Data Group review, 2025: the fields remain insufficiently constrained; nothing changes it.

Claim 52 · checked 24 September 2026 · AI-assisted audit

Claim: Auger puts typical deflections across the galaxy at a few tens of degrees for a particle of 10 exa-electronvolts per unit of charge.

Kind
What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

A figure from models of the galaxy’s field, which Auger says are not well constrained by data; it depends on direction.

Later work looked for

Unger and Farrar (2024) use newer galactic field models (UF23) and find the field uncertainty still comparable to the energy uncertainty in locating a source; nothing changes the figure.

Claim 53 · checked 24 September 2026 · AI-assisted audit

Claim: A cosmic ray’s arrival direction therefore carries a smeared memory of its origin rather than an address.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from claims 52 and 53.

Claim 54 · checked 24 September 2026 · AI-assisted audit

Claim: One way around this is to look for neutral messengers produced alongside them.

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

How the method works; not a finding later work revises.

Corrected

24 September 2026. Previously: “The way around this” Statistical anisotropy studies are another route (claims 33 to 35), so neutral messengers are one way, not the way.

Claim 55 · checked 24 September 2026 · AI-assisted audit

Claim: In 2017 a neutrino of about 290 tera-electronvolts, detected under the Antarctic ice, arrived from the direction of a blazar that was flaring in gamma rays, and telescopes from radio to gamma rays followed it up.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

The neutrino energy is a most probable value; the 90 per cent lower limit is 183 TeV.

Later work looked for

Particle Data Group review, 2025: an archival excess from the same blazar at 3.5 standard deviations and an excess from NGC 1068 at 4.2; page updated (claim 58).

Corrected

24 September 2026. Previously: “In 2017 a high-energy neutrino detected under the Antarctic ice was traced to a flaring blazar, and telescopes across the spectrum confirmed the flare.” "Traced to" overstated a positional coincidence that the IceCube team puts at three standard deviations and says needs further observations "to unambiguously establish" a correlation.

Claim 56 · checked 24 September 2026 · AI-assisted audit

Claim: The IceCube team disfavoured a chance coincidence at the level of three standard deviations.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

Three standard deviations, in models where neutrino production follows gamma-ray production.

Later work looked for

Particle Data Group review, 2025: reports the same 3 standard deviations; nothing changes it.

Claim 57 · checked 24 September 2026 · AI-assisted audit

Claim: Archival data later showed an earlier excess of neutrinos from the same blazar, and a second galaxy, NGC 1068, has since shown an excess of neutrinos at 4.2 standard deviations.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.4.4

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: Subsequent analyses of archival data revealed an excess in neutrino events with a significance of 3.5σ with respect to the expected atmospheric background, coincident with the position of TXS 0506+056, albeit not correlated with an electromagnetic flare

    Notation restored: Spacing restored from the review’s PDF (1 December 2025) rendered with pdftotext -layout, read 2026-09-24. The text as extracted reads: Subsequent analyses of archival data revealed an excess in neutrino events with a significance of 3.5σwith respect to the expected atmospheric background, coincident with the position of TXS0506+056, albeit not correlated with an electromagnetic flare

  • Supports

    Cosmic Rays (Review of Particle Physics, chapter 30)section 30.4.4

    Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Reference work

    The source reads: An excess of 79⁺²²₋₂₀ neutrinos was found in the direction of the nearby AGN NGC 1068 (not a blazar, but a Seyfert-2 galaxy), at a significance of 4.2σ

    Notation restored: Spacing, superscript and subscript restored from the review’s PDF (1 December 2025) rendered with pdftotext -layout, read 2026-09-24. The text as extracted reads: An excess of79+22 −20 neutrinos was found in the direction of the nearby AGN NGC1068 (not a blazar, but a Seyfert-2 galaxy), at a significance of 4.2σ

What this does not establish

Taken from the Particle Data Group review; the IceCube papers behind it were not read here. The review notes that a follow-up with more data confirmed the NGC 1068 excess at lower significance. Neither links neutrinos to the highest-energy cosmic rays.

Later work looked for

Particle Data Group review, revised October 2025, is the newer work; page updated.

Corrected

24 September 2026. Previously: “” Added. "It is one event" was out of date: the Particle Data Group review (2025) reports both.

Claim 58 · checked 24 September 2026 · AI-assisted audit

Claim: That is the closest anyone has come to catching a source in the act

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from claims 56 to 58: the only associations with individual objects are through neutrinos, and none reaches five standard deviations in these sources.

Claim 59 · checked 24 September 2026 · AI-assisted audit

Claim: and it does not reach the extreme end: the 2017 neutrino points to protons or nuclei of at least tens of peta-electronvolts.

Kind
What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922Aintroduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Model

    The source reads: An association of observed astrophysical neutrinos with blazars would therefore imply that high-energy protons or nuclei up to energies of at least tens of PeV are produced in blazar jets, suggesting that they may be the birthplaces of the most energetic particles observed in the Universe

What this does not establish

Tens of peta-electronvolts is about 10^16 eV, four orders of magnitude below the extreme events. IceCube notes blazars "may be" the birthplaces of the most energetic particles; that is a suggestion, not a finding.

Later work looked for

Particle Data Group review, 2025: no neutrino or photon has yet been tied to the highest-energy cosmic rays; nothing changes it.

Corrected

24 September 2026. Previously: “and it is one event.” The page implied the neutrino caught an accelerator of the particles it is about. The IceCube paper’s own inference is to protons or nuclei of at least tens of PeV, far below the extreme end.

Claim 60 · checked 24 September 2026 · AI-assisted audit

The ones from an empty sky

Claim: The ones from an empty sky

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: A messenger that forgets its route on the way.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

An image for the magnetic deflection described in claims 52 and 53.

Claim 62 · checked 24 September 2026 · AI-assisted audit

The particles that arrive from nowhere

Claim: The particles that arrive from nowhere

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Figurative: the directions of the 1991 and 2021 events show no identified source (claims 64 and 65), not an empty origin.

Claim 63 · checked 24 September 2026 · AI-assisted audit

Claim: The 2021 event reported by the Telescope Array arrived from a direction pointing back at a void in the large-scale structure of the universe.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    An extremely energetic cosmic ray observed by a surface detector arrayabstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: Its arrival direction points back to a void in the large-scale structure of the Universe. Possible explanations include a large deflection by the foreground magnetic field, an unidentified source in the local extragalactic neighborhood or an incomplete knowledge of particle physics.

  • Qualifies

    Where did the Amaterasu particle come from?abstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Model

    The source reads: We estimate a localization uncertainty on the source direction of 6.6% of 4 π or 2726 deg 2.

What this does not establish

The arrival direction, not the source direction: back-tracked through the galaxy’s field the likely source region covers about 6.6 per cent of the sky, according to Unger and Farrar.

Later work looked for

Crossref, 2024 on, "Amaterasu": Unger and Farrar (2024) find the source direction uncertain over 6.6 per cent of the sky; recorded in limits and on the page (claim 68).

Claim 64 · checked 24 September 2026 · AI-assisted audit

Claim: The 1991 event had the same problem: Elbert and Sommers searched its arrival direction and found no likely source within 50 megaparsecs.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    In search of a source for the 320 EeV Fly’s Eye cosmic rayabstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Observational study: associations, not causes

    The source reads: Our search finds no likely source within 50 Mpc in the direction from which the particle arrived.

Other readings

Elbert and Sommers themselves weighed a nearby galaxy such as M82, a non-standard particle, and strong magnetic deflection from a nearby radio galaxy.

Corrected

24 September 2026. Previously: “The same was true of the 1991 event:” Elbert and Sommers report no likely source, not a void; "the same was true" said more.

Claim 65 · checked 24 September 2026 · AI-assisted audit

Claim: Either the particle was bent far more than models of the galaxy’s magnetic field allow, because it was a heavy nucleus or the fields are stronger than modelled, or a nearby source has gone unidentified, or the physics of particles at these energies is not fully known.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    An extremely energetic cosmic ray observed by a surface detector arrayabstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: Its arrival direction points back to a void in the large-scale structure of the Universe. Possible explanations include a large deflection by the foreground magnetic field, an unidentified source in the local extragalactic neighborhood or an incomplete knowledge of particle physics.

  • Supports

    An extremely energetic cosmic ray observed by a surface detector arrayDistribution of other TA events

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement

    The source reads: The lack of a nearby source for the 244 EeV event could be due to larger magnetic deflections than predicted by the GMF models caused by a heavy primary particle or stronger magnetic fields than in the models. Alternatively, super-GZK UHECRs could be indicating an incomplete understanding

Other readings

These are the Telescope Array’s three possibilities. Later work favours the first (claim 68).

Corrected

24 September 2026. Previously: “Either the deflections are much larger than the models say, or the local magnetic field structure is wrong, or these particles are not ordinary protons, or something is producing them that nobody has identified.” The page gave four options where the paper gives three, and "not ordinary protons" ran together a heavy nucleus, which is ordinary physics, with new particle physics. Now the paper’s own list.

Claim 66 · checked 24 September 2026 · AI-assisted audit

Claim: The Telescope Array paper listed these rather than choosing.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

Corrected

24 September 2026. Previously: “The paper reporting the second one said as much rather than choosing.” Names the paper, now that the sentence before is reordered.

Claim 67 · checked 24 September 2026 · AI-assisted audit

Claim: A later analysis by Unger and Farrar took it for an iron nucleus, found that it then fits the usual picture, and proposed a brief outburst in an otherwise ordinary galaxy no more than 50 megaparsecs away.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Where did the Amaterasu particle come from?abstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Model

    The source reads: Interpreted as a primary iron nucleus or slightly stripped fragment, the event fits well within the existing paradigm for UHECR composition and spectrum.

  • Supports

    Where did the Amaterasu particle come from?section 6

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Model

    The source reads: we conclude it was produced by a source whose distance is within 8 Mpc, or up to 50 Mpc, depending on its energy.

  • Supports

    Where did the Amaterasu particle come from?section 6

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Model

    The source reads: The most straightforward explanation for Amaterasu seems to be that it was produced by a transient in an otherwise ordinary galaxy.

Other readings

The Telescope Array’s classifier favoured a proton over a photon but could not tell a proton from a heavier nucleus. Unger and Farrar say a proton would demand an entirely new kind of source. Their reading is a proposal, not an identification.

Later work looked for

Crossref, 2024 on, "Amaterasu": further proposals include blazars and exotic particles; none settles it.

Corrected

24 September 2026. Previously: “” Added. A published analysis offers a reading within standard physics, and the page presented the question as untouched since 2023.

Claim 68 · checked 24 September 2026 · AI-assisted audit

What was read