Evidence record

Where does the solar system end?

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: 34
A judgement, not a fact: 16
Partly checked: 26

If something here is wrong, misquoted, out of date or unfair, write to support@unknownoceans.com and give the claim number, which does not change.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

A definitional question with measurements inside it. One of its three answers, the heliopause, has been crossed and measured; the other two are a matter of which objects count and how far the Sun’s gravity holds them, and the outermost rests on inference from comet orbits.

The solar system has one edge
Contested
The page’s argument is that it has at least three, depending on what the solar system is taken to be.
The heliopause is a physical surface that can be located
Established
Both Voyagers crossed it and measured the density jump pressure balance predicts.
The Oort cloud exists
Open
Oort inferred it from comet orbits in 1950; NASA describes it as theorized and gives its extent; no object has been seen in its outer part.

How the question is labelled

Claim: The edge of the wind

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

Claim: Solar edge

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

The question

Claim: Two spacecraft have crossed a boundary.

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
Where Are Voyager 1 and Voyager 2 Now?Voyager 1 section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: Voyager 1 and its twin, Voyager 2, are the only spacecraft to ever operate outside the heliosphere, or the protective bubble of particles and magnetic fields generated by the Sun.
Supports
Voyager 2 observations near the heliopausesection 1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: Voyager 2 (V2) crossed the heliopause (HP) on Nov. 5 2018 when it was 119 AU from the Sun at a heliolatitude of 31° S

Later work looked for

Crossref, 2020 on, "Voyager heliopause interstellar plasma density": Gurnett and Kurth (2020) give the same crossing dates and distances; nothing that changes them.

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

Claim: Whether that boundary is the edge depends on what you think the solar system is.

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.

The page’s framing of its question. It follows from the three definitions set out under "Which boundary counts".

Context
Oort Cloud: Factsopening and distance sections
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The inner edge of the Oort Cloud, however, is thought to be located between 2,000 and 5,000 AU from the Sun, with the outer edge being located somewhere between 10,000 and 100,000 AU from the Sun.

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

Claim: There are three defensible answers,

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.

The page’s judgement. The three are the planets, the heliopause and the gravitational reach of the Oort cloud, each set out and sourced under "Which boundary counts".

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

Claim: and the outermost lies hundreds to thousands of times further out than the innermost

Kind: Present-day figure. A count, survey or report finding, as the named source gives it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Neptune’s orbit is at 30 au; NASA puts the Oort cloud’s outer edge at 10,000 to 100,000 au, which is about 330 to 3,300 times further.

Supports
A Sedna-like body with a perihelion of 80 astronomical unitsabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: the rocky terrestrial planets including the asteroids at 0.39 to 4.2 astronomical units (au) from the Sun ... the gas giant planets at 5 to 30 au from the Sun, and the icy Kuiper belt objects at 30 to 50 au from the Sun.
Supports
Oort Cloud: Factsdistance section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Reference work
The source reads: The inner edge of the Oort Cloud, however, is thought to be located between 2,000 and 5,000 AU from the Sun, with the outer edge being located somewhere between 10,000 and 100,000 AU from the Sun.
Supports
Oort Cloud: Factsdistance section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: about 4.5 hours to reach Neptune’s orbit
4.5 light-hours is about 32 au (light takes about 8.3 minutes per au). With the planets ending at about 30 au and the Oort cloud’s outer edge put at 10,000 to 100,000 au, the ratio runs from about 300 to about 3,000; taking the Kuiper belt’s 50 au as the first answer gives 200 to 2,000. Hundreds to thousands either way.

What this does not establish

The outer figure is an inference, not a measurement: no object has been seen in the outer Oort cloud. Trujillo and Sheppard, for the planets, was read as an abstract.

Later work looked for

NASA’s own current page, read on the access date, is the newest statement of the figure; Crossref, 2020 on, "Oort cloud outer edge extent": nothing that changes it.

Corrected

24 September 2026. Previously: “they differ by a factor of a thousand” From the planets at 30 au to an outer edge that NASA places at 10,000 to 100,000 au is a factor of roughly 330 to 3,300, not one factor of a thousand.

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

Claim: One is where the planets stop, one is where the Sun’s wind stops, and one is where the Sun’s gravity stops holding on.

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.

Three definitions of the solar system, each taken up in "Which boundary counts".

Context
Oort Cloud: Factsdistance section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: the heliopause, where the solar wind – a torrent of charged particles flowing away from the Sun at about a million miles per hour (400 kilometers per second) – smooshes up against the interstellar medium. Beyond this boundary is interstellar space, where the Sun’s magnetic field holds no sway.

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

Claim: Spacecraft have passed the first and two have crossed the second.

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

Both Voyagers crossed the heliopause at about 120 au, four times Neptune’s distance, so both have passed the planets as well.

Supports
Voyager 2 observations near the heliopausesection 1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: V1 crossed the HP in August 2012 at 121.7 AU
Supports
Voyager 2 observations near the heliopausesection 1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Voyager 2 (V2) crossed the heliopause (HP) on Nov. 5 2018 when it was 119 AU from the Sun at a heliolatitude of 31° S
Supports
Where Are Voyager 1 and Voyager 2 Now?Voyager 1 section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: Voyager 1 and its twin, Voyager 2, are the only spacecraft to ever operate outside the heliosphere, or the protective bubble of particles and magnetic fields generated by the Sun.
Context
A Sedna-like body with a perihelion of 80 astronomical unitsabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: the rocky terrestrial planets including the asteroids at 0.39 to 4.2 astronomical units (au) from the Sun ... the gas giant planets at 5 to 30 au from the Sun, and the icy Kuiper belt objects at 30 to 50 au from the Sun.

Later work looked for

Crossref, 2020 on, "Voyager heliopause interstellar plasma density": Gurnett and Kurth (2020) give the same crossing dates and distances; nothing that changes them.

Corrected

24 September 2026. Previously: “Only the middle one has ever been visited.” Spacecraft passed the planets long before the heliopause, so the first boundary has been passed too. The sentence now says what has been reached and gives NASA’s figure for the third.

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

Claim: The third is tens of thousands of years away at Voyager 1’s speed.

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
Oort Cloud: Factsdistance section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Reference work
The source reads: At its current speed of about a million miles a day, NASA's Voyager 1 spacecraft won't enter the Oort Cloud for about 300 years. And it won’t exit the outer edge for maybe 30,000 years.

What this does not establish

NASA’s "maybe 30,000 years" rests on an outer edge whose distance is itself uncertain.

Later work looked for

NASA’s own current page, read on the access date, is the newest statement of the figure; Crossref, 2020 on, "Oort cloud outer edge extent": nothing that changes it.

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

Claim: The Sun does not simply sit in space.

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

Claim: It blows, continuously, a thin supersonic wind of charged particles in every direction, and that wind carves out a bubble in the gas between the stars.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

"Thin" is the density Gurnett and others give for the outer heliosphere, about 0.002 particles per cubic centimetre.

Supports
Oort Cloud: Factsdistance section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Reference work
The source reads: the heliopause, where the solar wind – a torrent of charged particles flowing away from the Sun at about a million miles per hour (400 kilometers per second) – smooshes up against the interstellar medium. Beyond this boundary is interstellar space, where the Sun’s magnetic field holds no sway.
Supports
A small and round heliosphere suggested by magnetohydrodynamic modelling of pick-up ionsabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Model
The source reads: The shape of the solar wind bubble within the interstellar medium, the so-called heliosphere, has been explored over six decades ... through charge-exchange with the supersonic solar wind
Supports
In Situ Observations of Interstellar Plasma with Voyager 1abstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: The boundary, called the heliopause, is expected to be marked by a large increase in plasma density, from about 0.002 per cubic centimeter (cm(-3)) in the outer heliosphere, to about 0.1 cm(-3) in the interstellar medium.

What this does not establish

Gurnett and others (2013) was read as an abstract.

Later work looked for

Crossref, 2020 on, "solar wind heliosphere": a description of the solar wind, not a figure later work revises.

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

Claim: Somewhere the bubble ends.

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

Claim: Voyager 1 went through it in 2012 and Voyager 2 in 2018,

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.

Supports
Voyager 2 observations near the heliopausesection 1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: V1 crossed the HP in August 2012 at 121.7 AU
Supports
Voyager 2 observations near the heliopausesection 1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Voyager 2 (V2) crossed the heliopause (HP) on Nov. 5 2018 when it was 119 AU from the Sun at a heliolatitude of 31° S
Qualifies
A Foreshock Model for Interstellar Shocks of Solar Origin: Voyager 1 and 2 Observationsabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: V1 reached the heliopause on 2012 August 25, at 121.6 au, and V2 reached the heliopause on 2018 November 5, at 119.0 au.
Gives 121.6 au for Voyager 1 where Richardson gives 121.7.

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

Claim: and the argument over whether the first had really done so

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.

Supports
Voyager 2 observations near the heliopausesection 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: The V1 HP crossing was initially controversial because, although the magnetic field magnitude B and galactic cosmic ray (GCR) intensities increased and the anomalous cosmic ray (ACR) intensities decreased as predicted, the magnetic field direction did not change as was expected
Supports
Voyager 2 observations near the heliopausesection 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The V2 HP crossing was similar enough to the V1 crossing that it was immediately recognized that V2 had entered the VLISM.

Corrected

24 September 2026. Previously: “the argument over whether they had really done so” Only Voyager 1’s crossing was argued over; Richardson and others say Voyager 2’s was recognised at once.

Claim 14 · checked 24 September 2026 · AI-assisted audit

Claim: is a good demonstration of how hard it is to recognise a border with no posts.

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.

The page’s reading of the Voyager 1 dispute, told under "The crossing was not obvious from inside it".

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

What the instruments recorded

Claim: What the instruments recorded

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

The Sun blows a bubble

Claim: The Sun blows a bubble

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
Where Are Voyager 1 and Voyager 2 Now?Voyager 1 section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Reference work
The source reads: Voyager 1 and its twin, Voyager 2, are the only spacecraft to ever operate outside the heliosphere, or the protective bubble of particles and magnetic fields generated by the Sun.
Supports
A small and round heliosphere suggested by magnetohydrodynamic modelling of pick-up ionsabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Model
The source reads: The shape of the solar wind bubble within the interstellar medium, the so-called heliosphere, has been explored over six decades

Later work looked for

Crossref, 2020 on, "heliosphere": the bubble itself is not in question; its shape is, as the page says later.

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

Claim: The solar wind streams outward until its pressure no longer exceeds the pressure of the interstellar medium it is pushing into.

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.

Context
Plasma densities near and beyond the heliopause from the Voyager 1 and 2 plasma wave instrumentsabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Theory · Model
The source reads: The heliopause is the boundary between the hot heliospheric (solar wind) plasma and the relatively cold interstellar plasma. Pressure balance considerations show that there should be a large (factor of 20 to 50) density increase across the heliopause.
Read as an abstract; the claim rests on Gurnett and Kurth (2020) and the NASA page.
Supports
Oort Cloud: Factsdistance section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: the heliopause, where the solar wind – a torrent of charged particles flowing away from the Sun at about a million miles per hour (400 kilometers per second) – smooshes up against the interstellar medium. Beyond this boundary is interstellar space, where the Sun’s magnetic field holds no sway.
Qualifies
A small and round heliosphere suggested by magnetohydrodynamic modelling of pick-up ionsdiscussion
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: still somewhat larger than the observations (95AU at V1 and 85AU at
The wind first slows at a termination shock, which the Voyagers crossed well inside the heliopause.
Supports
A Foreshock Model for Interstellar Shocks of Solar Origin: Voyager 1 and 2 Observationssection 2, discussion of figure 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: This large density jump is a consequence of pressure balance between the hot plasma inside the heliosphere and the relatively much cooler plasma in the interstellar medium.

What this does not establish

A simplification: the wind is slowed first at a termination shock, crossed at about 95 au by Voyager 1 and 85 au by Voyager 2, and the heliopause lies beyond the slowed wind. Gurnett and Kurth (2019) was read as an abstract; Gurnett and Kurth (2020), read in full, carries the pressure balance.

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

Claim: The surface where the two balance is the heliopause, and inside it the environment is governed by the Sun rather than by the galaxy.

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.

Context
Plasma densities near and beyond the heliopause from the Voyager 1 and 2 plasma wave instrumentsabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: The heliopause is the boundary between the hot heliospheric (solar wind) plasma and the relatively cold interstellar plasma. Pressure balance considerations show that there should be a large (factor of 20 to 50) density increase across the heliopause.
Supports
Oort Cloud: Factsdistance section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: the heliopause, where the solar wind – a torrent of charged particles flowing away from the Sun at about a million miles per hour (400 kilometers per second) – smooshes up against the interstellar medium. Beyond this boundary is interstellar space, where the Sun’s magnetic field holds no sway.
Supports
A Foreshock Model for Interstellar Shocks of Solar Origin: Voyager 1 and 2 Observationsabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: reach the heliopause, the boundary between the hot solar plasma and the relatively cool interstellar plasma

What this does not establish

Gurnett and Kurth (2019) was read as an abstract; Gurnett and Kurth (2020), read in full, and the NASA page carry the definition.

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

Claim: That is a physical boundary rather than a cartographic one, which is why it can be detected by an instrument rather than agreed by a committee.

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 the pressure balance and density jump the next sentence cites.

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

Claim: Pressure balance requires the plasma density to jump by a factor of twenty to fifty across it,

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Plasma densities near and beyond the heliopause from the Voyager 1 and 2 plasma wave instrumentsabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Theory · Model
The source reads: The heliopause is the boundary between the hot heliospheric (solar wind) plasma and the relatively cold interstellar plasma. Pressure balance considerations show that there should be a large (factor of 20 to 50) density increase across the heliopause.

What this does not establish

The twenty to fifty is Gurnett and Kurth’s range from pressure balance, a prediction; the jump Voyager 2 measured was about twenty. The paper was read as an abstract.

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

Claim: which is what makes it something a spacecraft can measure.

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 the density jump, which both Voyagers’ plasma wave instruments measured.

Claim 22 · checked 24 September 2026 · AI-assisted audit

The crossing was not obvious from inside it

Claim: The crossing was not obvious from inside it

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.

Supports
Voyager 2 observations near the heliopausesection 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The V1 HP crossing was initially controversial because, although the magnetic field magnitude B and galactic cosmic ray (GCR) intensities increased and the anomalous cosmic ray (ACR) intensities decreased as predicted, the magnetic field direction did not change as was expected

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

Claim: In August 2012 Voyager 1 was about 18.5 billion kilometres from the Sun.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Search for the exit: Voyager 1 at heliosphere’s border with the galaxyabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: Particles of solar origin at Voyager 1, located at 18.5 billion kilometers (123 astronomical units) from the Sun, decreased by a factor of >10(3) on 25 August 2012, while those of galactic origin (cosmic rays) increased by 9.3% at the same time.
Supports
Search for the exit: Voyager 1 at heliosphere’s border with the galaxyScience editor’s summary
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: In August last year, the Voyager 1 spacecraft, which was launched 35 years ago, was 18.5 billion kilometers away from the Sun

What this does not establish

Read as an abstract and editor’s summary; the paper was not read.

Later work looked for

Crossref, 2020 on, "Voyager heliopause interstellar plasma density": Gurnett and Kurth (2020) give the same crossing dates and distances; nothing that changes them.

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

Claim: Its particle detectors recorded a sharp boundary being crossed five times in roughly thirty days:

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Search for the exit: Voyager 1 at heliosphere’s border with the galaxyScience editor’s summary
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: report observations of energetic ions and electrons by Voyager 1 that suggest that a sharp and distinct boundary was crossed five times over ∼30 days.
Supports
Magnetic field observations as Voyager 1 entered the heliosheath depletion regionabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: Magnetic fields measured by Voyager 1 (V1) show that the spacecraft crossed the boundary of an unexpected region five times between days 210 and ~238 in 2012.

What this does not establish

Read as abstracts and Science’s editor’s summary; the papers were not read. The five crossings between days 210 and about 238 are Burlaga and others’ magnetometer count.

Later work looked for

Crossref, 2014 on, "whether Voyager 1 has crossed the heliopause": Gloeckler and Fisk (2014, 2015) argued it was still inside; Richardson and others (2020) and Gurnett and Kurth (2020) treat the 2012 crossing as settled, and Voyager 2 crossed the same way in 2018. Page now says "for most of the field".

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

Claim: ions from inside fell away, and galactic cosmic rays from outside rose.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Search for the exit: Voyager 1 at heliosphere’s border with the galaxyabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: Particles of solar origin at Voyager 1, located at 18.5 billion kilometers (123 astronomical units) from the Sun, decreased by a factor of >10(3) on 25 August 2012, while those of galactic origin (cosmic rays) increased by 9.3% at the same time.
Supports
Voyager 1 Observes Low-Energy Galactic Cosmic Rays in a Region Depleted of Heliospheric Ionsabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: the steady intensity of low-energy ions it had observed for the previous 6 years suddenly dropped for a third time and soon completely disappeared as the ions streamed away into interstellar space ... the intensity of cosmic ray nuclei from outside the heliosphere abruptly increased

What this does not establish

Read as abstracts; the papers were not read.

Later work looked for

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

Claim: The magnetic field, though, did not change direction at any of those crossings,

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Magnetic field observations as Voyager 1 entered the heliosheath depletion regionabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: The direction of B did not change significantly across any of the five boundary crossings
Supports
Voyager 2 observations near the heliopausesection 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The V1 HP crossing was initially controversial because, although the magnetic field magnitude B and galactic cosmic ray (GCR) intensities increased and the anomalous cosmic ray (ACR) intensities decreased as predicted, the magnetic field direction did not change as was expected

What this does not establish

Burlaga and others (2013) was read as an abstract; Richardson and others (2020), read in full, reports the same.

Later work looked for

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

Claim: which is what a passage into interstellar space was expected to look like.

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.

The expectation was a change of direction at the heliopause, which did not come.

Supports
Voyager 2 observations near the heliopausesection 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The V1 HP crossing was initially controversial because, although the magnetic field magnitude B and galactic cosmic ray (GCR) intensities increased and the anomalous cosmic ray (ACR) intensities decreased as predicted, the magnetic field direction did not change as was expected

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

Claim: For a year the same data supported two readings: the spacecraft was out, or the spacecraft was in an unexpected layer of the bubble where particles could flow both ways.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Burlaga and others read the data as a "magnetic highway" inside the heliosphere; the question was settled for most of the field by Gurnett and others in September 2013.

Supports
Magnetic field observations as Voyager 1 entered the heliosheath depletion regionScience editor’s summary
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: indicating that Voyager 1 had not crossed the heliopause but had entered a region in the heliosphere that serves as a magnetic highway along which low-energy ions from inside stream away and galactic cosmic rays flow in from interstellar space
Supports
In Situ Observations of Interstellar Plasma with Voyager 1Science editor’s summary
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: Last summer, it was not clear if the Voyager 1 spacecraft had finally crossed the heliopause
Supports
Voyager 2 observations near the heliopausesection 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The V1 HP crossing was initially controversial because, although the magnetic field magnitude B and galactic cosmic ray (GCR) intensities increased and the anomalous cosmic ray (ACR) intensities decreased as predicted, the magnetic field direction did not change as was expected

What this does not establish

The Science papers were read as abstracts and editor’s summaries.

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

Claim: For most of the field it was settled by a different instrument.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Voyager 2 observations near the heliopausesection 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Plasma oscillations observed beyond the boundary showed that the electron densities were much higher than those in the heliosheath (HSH) indicating that V1 had crossed the HP ... V1 has remained in the VLISM since 2012.
Supports
In Situ Observations of Interstellar Plasma with Voyager 1abstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: These and other observations provide strong evidence that Voyager 1 has crossed the heliopause into the nearby interstellar plasma.
Qualifies
A test for whether or not Voyager 1 has crossed the heliopauseabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Argument
The source reads: The evidence is unclear, however, as to whether Voyager 1 has crossed the heliopause into the local interstellar medium or remains within the heliosheath.
Supports
A Foreshock Model for Interstellar Shocks of Solar Origin: Voyager 1 and 2 Observationssection 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: The oscillation frequency for the 2012 October–November plasma oscillation event provided the first definitive confirmation that V1 crossed the heliopause into the interstellar medium on or about 2012 August 25

What this does not establish

Not everyone agreed. Gloeckler and Fisk argued in 2014 that the evidence was unclear and that Voyager 1 might still be inside, and proposed a test. Their paper and Gurnett and others (2013) were read as abstracts. That most of the field accepted the plasma wave result is read from the later literature, Richardson and others (2020) and Gurnett and Kurth (2020), which treat it as settled; no survey of opinion was read.

Later work looked for

Corrected

24 September 2026. Previously: “It was settled by a different instrument.” Gloeckler and Fisk (2014) disputed the crossing after the plasma wave result; the page now says most of the field, not all of it, took it as settled.

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

Claim: When the Sun threw out a disturbance, the plasma around Voyager 1 rang, and the frequency of that ringing gives the density of the plasma directly.

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

"Rang" is the page’s word for electron plasma oscillations; their frequency gives the electron density.

Supports
A Foreshock Model for Interstellar Shocks of Solar Origin: Voyager 1 and 2 Observationsabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: One of their remarkable discoveries was the detection of shocks propagating into the interstellar plasma from energetic solar events. These shocks are typically preceded by electron plasma oscillations ... The frequencies of the plasma oscillations have now provided radial electron density profiles in the outer heliosphere and in the interstellar medium
Context
In Situ Observations of Interstellar Plasma with Voyager 1abstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: This oscillation frequency corresponds to an electron density of about 0.08 cm(-3), very close to the value expected in the interstellar medium.
Read as an abstract; the claim rests on Gurnett and Kurth (2020), read in full.
Supports
Voyager 2 observations near the heliopausesection 5
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: PWS observations show plasma oscillations before the current increase at day 420, suggesting that this current increase is related to the shock that generates these oscillations
Supports
A Foreshock Model for Interstellar Shocks of Solar Origin: Voyager 1 and 2 Observationssection 1, Introduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: shocks propagating outward from energetic disturbances at the Sun were continuing into the VLISM

What this does not establish

Gurnett and others (2013) was read as an abstract; Gurnett and Kurth (2020), read in full, carries the claim.

Later work looked for

Crossref, 2020 on, "Voyager heliopause interstellar plasma density": Gurnett and Kurth (2020) give the same crossing dates and distances; nothing that changes them.

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

Claim: Two episodes of it, in late 2012 and again in 2013, measured a density characteristic of interstellar space rather than of the solar wind.

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

Context
In Situ Observations of Interstellar Plasma with Voyager 1Science editor’s summary
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: evidence that the spacecraft was in the interstellar plasma during two periods, October to November 2012 and April to May 2013
Read as an abstract and editor’s summary; the claim rests on Gurnett and Kurth (2020), read in full.
Context
In Situ Observations of Interstellar Plasma with Voyager 1abstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: This oscillation frequency corresponds to an electron density of about 0.08 cm(-3), very close to the value expected in the interstellar medium.
Supports
A Foreshock Model for Interstellar Shocks of Solar Origin: Voyager 1 and 2 Observationssection 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: The oscillation frequency for the 2012 October–November plasma oscillation event provided the first definitive confirmation that V1 crossed the heliopause ... This density was consistent with the plasma density expected in the VLISM ... from the 2012 October–November event to the 2013 April–May event

What this does not establish

Gurnett and others (2013) was read as an abstract and editor’s summary; Gurnett and Kurth (2020), read in full, carries both episodes and the interstellar density.

Later work looked for

Crossref, 2020 on, "Voyager heliopause interstellar plasma density": Gurnett and Kurth (2020) give the same crossing dates and distances; nothing that changes them.

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

Claim: The same spacecraft, three instruments

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

Claim: Low-energy ions from the Sun disappear, galactic cosmic rays climb.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Voyager 1 Observes Low-Energy Galactic Cosmic Rays in a Region Depleted of Heliospheric Ionsabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: the steady intensity of low-energy ions it had observed for the previous 6 years suddenly dropped for a third time and soon completely disappeared as the ions streamed away into interstellar space ... the intensity of cosmic ray nuclei from outside the heliosphere abruptly increased
Supports
Search for the exit: Voyager 1 at heliosphere’s border with the galaxyabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: Particles of solar origin at Voyager 1, located at 18.5 billion kilometers (123 astronomical units) from the Sun, decreased by a factor of >10(3) on 25 August 2012, while those of galactic origin (cosmic rays) increased by 9.3% at the same time.

What this does not establish

Read as abstracts.

Later work looked for

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

Claim: Something was crossed. A boundary of some kind, five times.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Search for the exit: Voyager 1 at heliosphere’s border with the galaxyScience editor’s summary
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: report observations of energetic ions and electrons by Voyager 1 that suggest that a sharp and distinct boundary was crossed five times over ∼30 days.

What this does not establish

Read as Science’s editor’s summary.

Later work looked for

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

Claim: The magnetic field keeps its old direction across every crossing.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Magnetic field observations as Voyager 1 entered the heliosheath depletion regionabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: The direction of B did not change significantly across any of the five boundary crossings

What this does not establish

Read as an abstract.

Later work looked for

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

Claim: Not the heliopause as modelled. Perhaps a corridor inside it instead.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Burlaga and others’ reading at the time: a "heliosheath depletion region", which Science’s summary calls a magnetic highway.

Supports
Magnetic field observations as Voyager 1 entered the heliosheath depletion regionabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: The observations indicate that V1 entered a region of the heliosheath (the heliosheath depletion region), rather than the interstellar medium.
Supports
Magnetic field observations as Voyager 1 entered the heliosheath depletion regionScience editor’s summary
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: indicating that Voyager 1 had not crossed the heliopause but had entered a region in the heliosphere that serves as a magnetic highway along which low-energy ions from inside stream away and galactic cosmic rays flow in from interstellar space

What this does not establish

Read as an abstract and editor’s summary.

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

Claim: Plasma oscillations give a density like the interstellar medium.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
In Situ Observations of Interstellar Plasma with Voyager 1abstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: This oscillation frequency corresponds to an electron density of about 0.08 cm(-3), very close to the value expected in the interstellar medium.

What this does not establish

Read as an abstract.

Later work looked for

Crossref, 2020 on, "Voyager heliopause interstellar plasma density": Gurnett and Kurth (2020) give the same crossing dates and distances; nothing that changes them.

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

Claim: Outside.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
In Situ Observations of Interstellar Plasma with Voyager 1abstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: These and other observations provide strong evidence that Voyager 1 has crossed the heliopause into the nearby interstellar plasma.
Qualifies
A test for whether or not Voyager 1 has crossed the heliopauseabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: The evidence is unclear, however, as to whether Voyager 1 has crossed the heliopause into the local interstellar medium or remains within the heliosheath.

What this does not establish

Gurnett and others’ conclusion, which most of the field accepted and Gloeckler and Fisk (2014) disputed. Both read as abstracts.

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

Claim: The measurement that did not depend on what the field was expected to do.

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.

The page’s reading of why the density settled what the magnetic field could not.

Context
Voyager 2 observations near the heliopausesection 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Plasma oscillations observed beyond the boundary showed that the electron densities were much higher than those in the heliosheath (HSH) indicating that V1 had crossed the HP

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

Claim: Voyager 2’s cosmic ray instrument through 2018. The lower line is particles from inside the heliosphere and the upper line is galactic cosmic rays from outside it. On 5 November the first collapses and the second steps up, which is the crossing.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Describes NASA’s figure PIA22924, whose labels and date range were read on the image itself.

Supports
Cosmic ray measurements from Voyager 2 as it crossed into interstellar spaceabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: low-energy ions (>0.5 MeV per nucleon) originating inside the heliosphere and those of higher-energy Galactic cosmic rays (>70 MeV per nucleon) originating outside
Supports
Cosmic ray measurements from Voyager 2 as it crossed into interstellar spaceabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: On 5 November 2018, Voyager 2 observed a sharp decrease in the intensity of low-energy ions and a simultaneous increase in the intensity of cosmic rays, indicating that Voyager 2 had crossed the heliopause at 119 au and entered interstellar space about six years after Voyager 1.

What this does not establish

Stone and others (2019) was read as an abstract.

Later work looked for

Crossref, 2020 on, "Voyager heliopause interstellar plasma density": Gurnett and Kurth (2020) give the same crossing dates and distances; nothing that changes them.

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

And then it happened again

Claim: And then it happened again

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

Claim: Voyager 2 crossed on 5 November 2018 at 119 astronomical units, about six years after its twin.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Cosmic ray measurements from Voyager 2 as it crossed into interstellar spaceabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: On 5 November 2018, Voyager 2 observed a sharp decrease in the intensity of low-energy ions and a simultaneous increase in the intensity of cosmic rays, indicating that Voyager 2 had crossed the heliopause at 119 au and entered interstellar space about six years after Voyager 1.
Supports
Voyager 2 observations near the heliopausesection 1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Voyager 2 (V2) crossed the heliopause (HP) on Nov. 5 2018 when it was 119 AU from the Sun at a heliolatitude of 31° S

What this does not establish

Stone and others (2019) was read as an abstract; Richardson and others, read in full, gives the same date and distance.

Later work looked for

Crossref, 2020 on, "Voyager heliopause interstellar plasma density": Gurnett and Kurth (2020) give the same crossing dates and distances; nothing that changes them.

Claim 43 · checked 24 September 2026 · AI-assisted audit

Claim: This time a working plasma instrument sampled the interstellar plasma directly.

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
Voyager 2 observations near the heliopausesection 5
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: PLS observed VLISM plasma directly for the first time.

Later work looked for

Crossref, 2020 on, "Voyager heliopause interstellar plasma density": Gurnett and Kurth (2020) give the same crossing dates and distances; nothing that changes them.

Corrected

24 September 2026. Previously: “This time the plasma itself was measured rather than inferred.” Voyager 1’s plasma density was a measurement too, from plasma oscillations. What was new at Voyager 2 was a working plasma instrument, as Richardson and others say.

Claim 44 · checked 24 September 2026 · AI-assisted audit

Claim: Voyager 1’s had failed in 1980.

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.

Supports
Voyager 2 observations near the heliopausesection 1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The Voyager 1 (V1) plasma instrument failed in 1980, so V2 provides the first plasma data from the HP boundary regions

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

Claim: The plasma wave instruments on both spacecraft told the same story: a steep jump in density, about a factor of twenty at Voyager 2.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Plasma densities near and beyond the heliopause from the Voyager 1 and 2 plasma wave instrumentsabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: The first electron density measured by the Voyager 2 plasma wave instrument in the interstellar medium, 0.039 cm−3 ± 15%, was on 30 January 2019 at a heliocentric radial distance of 119.7 au. The density jump, about a factor of 20, confirms that Voyager 2 crossed the heliopause.
Supports
Plasma densities near and beyond the heliopause from the Voyager 1 and 2 plasma wave instrumentseditor’s summary
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: The Voyager 2 instrument recorded an electron density jump of a factor of 20, similar to that from Voyager 1 several years previously.
Supports
A Foreshock Model for Interstellar Shocks of Solar Origin: Voyager 1 and 2 Observationssection 2, discussion of figure 3
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: a gradient that is comparable to that observed by V1 almost eight years earlier
Voyager 1’s gradient, compared with Voyager 2’s.
Qualifies
A Foreshock Model for Interstellar Shocks of Solar Origin: Voyager 1 and 2 Observationssection 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: Note the large density increase from the TS to the interstellar plasma, about a factor of 50
For Voyager 1 the factor the paper gives runs from the termination shock, not across the heliopause alone.

What this does not establish

The factor of twenty is Voyager 2’s, from Gurnett and Kurth (2019), read as an abstract; for Voyager 1, Gurnett and Kurth (2020), read in full, give a comparable gradient and about fifty from the termination shock outward.

Later work looked for

Crossref, 2020 on, "Voyager heliopause interstellar plasma density": Gurnett and Kurth (2020) give the same crossing dates and distances; nothing that changes them.

Corrected

24 September 2026. Previously: “The plasma wave instruments gave the same result on both spacecraft: a density jump of about a factor of twenty, at 119.7 astronomical units for Voyager 2 and 122.6 for Voyager 1.” The two distances are where each spacecraft’s first interstellar density was measured, not where the jump happened: Voyager 2 crossed at 119 au and was at 119.7 by its first reading.

24 September 2026. Previously: “The plasma wave instruments on both spacecraft told the same story: a density jump of about a factor of twenty.” Integrity pass: the factor of twenty is Voyager 2's (Gurnett and Kurth 2019). For Voyager 1 the sources give a comparable gradient (Gurnett and Kurth 2020, read in full) and, from the termination shock to interstellar plasma, a factor of about fifty; neither gives Voyager 1 a factor of twenty across the heliopause.

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

Claim: Voyager 2’s first interstellar density was read at 119.7 astronomical units, Voyager 1’s at 122.6.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Plasma densities near and beyond the heliopause from the Voyager 1 and 2 plasma wave instrumentsabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: The first electron density measured by the Voyager 2 plasma wave instrument in the interstellar medium, 0.039 cm−3 ± 15%, was on 30 January 2019 at a heliocentric radial distance of 119.7 au. The density jump, about a factor of 20, confirms that Voyager 2 crossed the heliopause.
Supports
Plasma densities near and beyond the heliopause from the Voyager 1 and 2 plasma wave instrumentsabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: The new density is very similar to the first density measured in the interstellar medium by the Voyager 1 plasma wave instrument, 0.055 cm−3, on 23 October 2013 at a radial distance of 122.6 au.
Supports
A Foreshock Model for Interstellar Shocks of Solar Origin: Voyager 1 and 2 Observationssection 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: The electron plasma density inferred for this first event
The first Voyager 1 event, October to November 2012, gave 0.055 per cubic centimetre; the 2019 abstract’s 2013 is a slip. The distance, 122.6, is the 2019 abstract’s.

What this does not establish

The two distances are from Gurnett and Kurth (2019), read as an abstract. Gurnett and Kurth (2020), read in full, date Voyager 1’s first event to late 2012.

Later work looked for

Crossref, 2020 on, "Voyager heliopause interstellar plasma density": Gurnett and Kurth (2020) give the same crossing dates and distances; nothing that changes them.

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

Claim: Two independent crossings of the same surface is the strongest thing anyone can say about the heliopause,

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.

The page’s judgement of what two in-situ crossings are worth against models and remote sensing.

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

Claim: and it is the entire in-situ dataset.

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
Where Are Voyager 1 and Voyager 2 Now?Voyager 1 section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Reference work
The source reads: Voyager 1 and its twin, Voyager 2, are the only spacecraft to ever operate outside the heliosphere, or the protective bubble of particles and magnetic fields generated by the Sun.

Later work looked for

NASA’s page, current on the access date, is the newest statement; no other spacecraft has crossed.

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

What the boundary is

Claim: What the boundary is

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

Claim: A border recognised, in the end, by the density of the vacuum.

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.

For Voyager 1 the density was what settled it; Voyager 2’s crossing was recognised at once from its particles, field and plasma.

Context
Voyager 2 observations near the heliopausesection 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Plasma oscillations observed beyond the boundary showed that the electron densities were much higher than those in the heliosheath (HSH) indicating that V1 had crossed the HP ... The V2 HP crossing was similar enough to the V1 crossing that it was immediately recognized that V2 had entered the VLISM.

Corrected

24 September 2026. Previously: “A border you can only recognise by the density of the vacuum.” Richardson and others say Voyager 2’s crossing was recognised immediately from particles, field and plasma flow, so density is not the only way to recognise it.

Claim 51 · checked 24 September 2026 · AI-assisted audit

Which boundary counts

Claim: Which boundary counts

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

Claim: If the solar system is the region where the Sun’s wind dominates, it ends at about 120 times the Earth’s distance from the Sun, and two spacecraft have left it.

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
Voyager 2 observations near the heliopausesection 1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: Voyager 2 (V2) crossed the heliopause (HP) on Nov. 5 2018 when it was 119 AU from the Sun at a heliolatitude of 31° S
Supports
Voyager 2 observations near the heliopausesection 1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: V1 crossed the HP in August 2012 at 121.7 AU
Supports
Where Are Voyager 1 and Voyager 2 Now?Voyager 1 section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Voyager 1 and its twin, Voyager 2, are the only spacecraft to ever operate outside the heliosphere, or the protective bubble of particles and magnetic fields generated by the Sun.

Later work looked for

Crossref, 2020 on, "Voyager heliopause interstellar plasma density": Gurnett and Kurth (2020) give the same crossing dates and distances; nothing that changes them.

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

Claim: If it is the region where the Sun’s gravity dominates, it extends perhaps a hundred to a thousand times further,

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.

NASA’s outer edge of 10,000 to 100,000 au is roughly 80 to 800 times the heliopause’s 120; Oort’s own figures, 150,000 to 200,000 au, are over a thousand.

Supports
Oort Cloud: Factsdistance section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Reference work
The source reads: The inner edge of the Oort Cloud, however, is thought to be located between 2,000 and 5,000 AU from the Sun, with the outer edge being located somewhere between 10,000 and 100,000 AU from the Sun.
Against the heliopause at about 120 au, an outer edge of 10,000 to 100,000 au is about 80 to 830 times further; Oort’s 150,000 to 200,000 au would be 1,250 to 1,700. “A hundred to a thousand” is the round middle of that range, which the page marks with “perhaps”.
Supports
The structure of the cloud of comets surrounding the solar system, and a hypothesis concerning its originpages 92 and 95
Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Astronomical observation · Observational study: associations, not causes
The source reads: They must then form a huge cloud, extending, according to the numbers cited above, to distances of at least 150000 A.U., and possibly still further.
Supports
The structure of the cloud of comets surrounding the solar system, and a hypothesis concerning its originpage 95
Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026
The source reads: We see thus that the perturbative action of other stars puts a limit to the cloud at about 200000 A.U.

What this does not establish

Every figure for the outer edge is inferred from comet orbits; none is measured.

Later work looked for

Crossref, 2020 on, "Oort cloud outer edge extent" and "sednoid": no observation of the outer cloud; one more Sedna-like body (2023 KQ14) was reported by the FOSSIL II survey in 2025, consistent with a catalogue still being filled in.

Corrected

24 September 2026. Previously: “it extends perhaps a thousand times further, because comets on orbits that take millions of years are still bound to it.” NASA now puts the cloud’s outer edge at 10,000 to 100,000 au, which is 80 to 800 times the heliopause; the reason given for the comets being bound is now Oort’s own.

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

Claim: because comets that fall in from that far share the Sun’s motion and are bound to it.

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
The structure of the cloud of comets surrounding the solar system, and a hypothesis concerning its originpage 92
Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Astronomical observation · Observational study: associations, not causes
The source reads: This does not mean that they are interstellar. They belong very definitely to the solar system, because they share accurately the sun's motion.

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

Claim: Voyager 1 is not close to leaving that, and will not be for tens of thousands of years.

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
Oort Cloud: Factsdistance section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Reference work
The source reads: At its current speed of about a million miles a day, NASA's Voyager 1 spacecraft won't enter the Oort Cloud for about 300 years. And it won’t exit the outer edge for maybe 30,000 years.

Later work looked for

NASA’s own current page, read on the access date, is the newest statement of the figure; Crossref, 2020 on, "Oort cloud outer edge extent": nothing that changes it.

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

Claim: If it is simply where the objects are, the answer depends on which objects,

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.

The third definition, which the numbers below set out.

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

Claim: and the outer catalogue is still being filled in.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
A Sedna-like body with a perihelion of 80 astronomical unitsabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: Here we report the presence of a second Sedna-like object, 2012 VP113, whose perihelion is 80 au. The detection of 2012 VP113 confirms that Sedna is not an isolated object; instead, both bodies may be members of the inner Oort cloud

What this does not establish

Trujillo and Sheppard was read as an abstract. It shows one discovery in 2014; later finds are in the review note, not on this page.

Later work looked for

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

Claim: Three edges, in Earth-Sun distances

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

Claim: 30

Kind: Present-day figure. A count, survey or report finding, as the named source gives it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
A Sedna-like body with a perihelion of 80 astronomical unitsabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: the rocky terrestrial planets including the asteroids at 0.39 to 4.2 astronomical units (au) from the Sun ... the gas giant planets at 5 to 30 au from the Sun, and the icy Kuiper belt objects at 30 to 50 au from the Sun.

What this does not establish

Read as an abstract.

Later work looked for

Crossref, 2014 on: Neptune’s distance is not a figure later work revises.

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

Claim: Neptune

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

Claim: The outermost planet, and the inner edge of the Kuiper belt.

Kind: Present-day figure. A count, survey or report finding, as the named source gives it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
A Sedna-like body with a perihelion of 80 astronomical unitsabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: the rocky terrestrial planets including the asteroids at 0.39 to 4.2 astronomical units (au) from the Sun ... the gas giant planets at 5 to 30 au from the Sun, and the icy Kuiper belt objects at 30 to 50 au from the Sun.

What this does not establish

Read as an abstract.

Later work looked for

Crossref, 2014 on: nothing that moves the Kuiper belt’s inner edge.

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

Claim: ~120

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
Voyager 2 observations near the heliopausesection 1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: Voyager 2 (V2) crossed the heliopause (HP) on Nov. 5 2018 when it was 119 AU from the Sun at a heliolatitude of 31° S
Supports
Voyager 2 observations near the heliopausesection 1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: V1 crossed the HP in August 2012 at 121.7 AU

Later work looked for

Crossref, 2020 on, "Voyager heliopause interstellar plasma density": Gurnett and Kurth (2020) give the same crossing dates and distances; nothing that changes them.

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

Claim: Heliopause

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

Claim: Where the solar wind loses to the interstellar medium.

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.

Supports
Oort Cloud: Factsdistance section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: the heliopause, where the solar wind – a torrent of charged particles flowing away from the Sun at about a million miles per hour (400 kilometers per second) – smooshes up against the interstellar medium. Beyond this boundary is interstellar space, where the Sun’s magnetic field holds no sway.

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

Claim: Crossed twice.

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
Where Are Voyager 1 and Voyager 2 Now?Voyager 1 section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Reference work
The source reads: Voyager 1 and its twin, Voyager 2, are the only spacecraft to ever operate outside the heliosphere, or the protective bubble of particles and magnetic fields generated by the Sun.

Later work looked for

Crossref, 2020 on, "Voyager heliopause interstellar plasma density": Gurnett and Kurth (2020) give the same crossing dates and distances; nothing that changes them.

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

Claim: 10,000 to 100,000

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
Oort Cloud: Factsdistance section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Reference work
The source reads: The inner edge of the Oort Cloud, however, is thought to be located between 2,000 and 5,000 AU from the Sun, with the outer edge being located somewhere between 10,000 and 100,000 AU from the Sun.
Qualifies
The structure of the cloud of comets surrounding the solar system, and a hypothesis concerning its originpage 91, summary
Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026
The source reads: From a score of well-observed original orbits it is shown that the "new" long-period comets generally come from regions between about 50000 and 150000 A.U. distance. The sun must be surrounded by a general cloud of comets with a radius of this order
Qualifies
A Sedna-like body with a perihelion of 80 astronomical unitsabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: the as-yet unseen outer Oort cloud, some 10,000 AU from the Sun

What this does not establish

An inferred range. Oort’s 1950 estimate was larger, 50,000 to 150,000 au, and Trujillo and Sheppard give some 10,000.

Later work looked for

NASA’s own current page, read on the access date, is the newest statement of the figure; Crossref, 2020 on, "Oort cloud outer edge extent": nothing that changes it.

Corrected

24 September 2026. Previously: “~100,000” NASA’s current range for the outer edge; a single figure of 100,000 sat at its top and hid how uncertain the edge is.

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

Claim: Outer Oort cloud

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

Claim: Where NASA places the cloud’s outer edge.

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
Oort Cloud: Factsdistance section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Reference work
The source reads: The inner edge of the Oort Cloud, however, is thought to be located between 2,000 and 5,000 AU from the Sun, with the outer edge being located somewhere between 10,000 and 100,000 AU from the Sun.

Later work looked for

NASA’s own current page, read on the access date, is the newest statement of the figure; Crossref, 2020 on, "Oort cloud outer edge extent": nothing that changes it.

Corrected

24 September 2026. Previously: “” Added to say whose range the figure is.

Claim 69 · checked 24 September 2026 · AI-assisted audit

Claim: Inferred from the orbits of long-period comets, never observed directly.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
The structure of the cloud of comets surrounding the solar system, and a hypothesis concerning its originpage 91, summary
Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Astronomical observation · Observational study: associations, not causes
The source reads: From a score of well-observed original orbits it is shown that the "new" long-period comets generally come from regions between about 50000 and 150000 A.U. distance. The sun must be surrounded by a general cloud of comets with a radius of this order
Supports
A Sedna-like body with a perihelion of 80 astronomical unitsabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: the as-yet unseen outer Oort cloud, some 10,000 AU from the Sun

What this does not establish

Trujillo and Sheppard was read as an abstract.

Later work looked for

Claim 70 · checked 24 September 2026 · AI-assisted audit

What shape the bubble is

Claim: What shape the bubble is

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

Claim: Two crossings sample a large three-dimensional surface at two points.

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 plain statement of how little two crossings can sample.

Context
Voyager 2 observations near the heliopausesection 3
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The orientation of the HP at the V1 and V2 crossings may provide information on the global shape of the HP.

Corrected

24 September 2026. Previously: “Two crossings on roughly the same side of a large three-dimensional surface do not constrain its shape.” Richardson and others use the orientation of the heliopause at the crossings to argue it is blunt, so the crossings do constrain the shape, though they cannot settle it. "Roughly the same side" was not in any source read.

Claim 72 · checked 24 September 2026 · AI-assisted audit

Claim: The flows and magnetic field at Voyager 2’s crossing fit a blunt front,

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
Voyager 2 observations near the heliopausesection 3 and conclusions
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: Observations of the flows and magnetic field at the HP at V2 are consistent with models predicting a blunt HP.

Later work looked for

Crossref, 2020 on, "heliosphere shape tail croissant" and "three-dimensional map of the heliosphere IBEX": Powell and others (2024) call comet-like against croissant-like an ongoing controversy; Reisenfeld and others (2021) find the tail extends at least about 350 au, the limit of their method. Page now names who holds each side.

Claim 73 · checked 24 September 2026 · AI-assisted audit

Claim: but two points cannot settle the shape of the whole.

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.

Opher and others say future remote sensing and in-situ measurements will test the shape, which is to say the current ones have not settled it.

Context
A small and round heliosphere suggested by magnetohydrodynamic modelling of pick-up ionsdiscussion
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Future remote sensing and in-situ measurements will be able to test the reality of a rounder heliosphere.

Claim 74 · checked 24 September 2026 · AI-assisted audit

Claim: Models disagree about whether the heliosphere has a long tail like a comet, two lobes, or something closer to a croissant:

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
Magnetized jets driven by the Sun: the structure of the heliosphere revisitedabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Model
The source reads: The classic accepted view of the heliosphere is a quiescent, comet-like shape aligned in the direction of the Sun’s travel through the interstellar medium (ISM) extending for 1000s of AUs
Supports
Magnetized jets driven by the Sun: the structure of the heliosphere revisitedabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The interstellar wind blows the two jets into the tail but is not strong enough to force the lobes into a single comet-like tail
Supports
A small and round heliosphere suggested by magnetohydrodynamic modelling of pick-up ionsintroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Model
The source reads: There was a consensus, since the pioneering work of Baranov & Malama ... that the heliosphere shape is comet-like.
Supports
Lyα Absorption in a “Croissant-like” Heliosphereabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Model
The source reads: There is an ongoing controversy whether the heliosphere has a long “comet-like” tail or a short “croissant-like” tail.

What this does not establish

Three shapes from models, not observations; no image of the heliosphere’s tail exists.

Claim: the Boston University group’s model gives a short, croissant-like tail, and the Moscow group’s a long, comet-like one.

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
Lyα Absorption in a “Croissant-like” Heliosphereabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Model
The source reads: There is an ongoing controversy whether the heliosphere has a long “comet-like” tail or a short “croissant-like” tail. ... we compare the BU model, which presents a croissant-like tail, and the Moscow model, which presents a comet-like tail.
Supports
Lyα Absorption in a “Croissant-like” Heliosphereauthor affiliations
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Model
The source reads: Astronomy Department, Boston University, Boston, MA 02215, USA ... Lomonosov Moscow State University
Where the two models are made.

What this does not establish

Two models compared under identical boundary conditions; the paper finds neither matches the observed absorption in every direction.

Later work looked for

Corrected

24 September 2026. Previously: “” Added so that the page says who holds each side of a disagreement Powell and others call ongoing.

Claim 76 · checked 24 September 2026 · AI-assisted audit

Claim: The disagreement is not aesthetic.

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.

Introduces the consequences the next two sentences source.

Claim 77 · checked 24 September 2026 · AI-assisted audit

Claim: The models also differ on how large the bubble is,

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
A small and round heliosphere suggested by magnetohydrodynamic modelling of pick-up ionsabstract and discussion
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Model
The source reads: leading to a narrower HS and a smaller and rounder shape
Supports
A small and round heliosphere suggested by magnetohydrodynamic modelling of pick-up ionsdiscussion
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: An important scientific result of the new multi-ion model on top of the change in shape is the significant reduction in the thickness of the HS.

Later work looked for

Corrected

24 September 2026. Previously: “It changes how much interstellar material reaches the planets, and how that has varied over the millions of years the Sun has spent moving through denser and thinner regions of the galaxy.” No source cited or found says the shape of the heliosphere sets how much interstellar material reaches the planets. The passage now says what the models differ on, and reports the one published simulation of the Sun meeting a denser cloud, as a simulation.

Claim 78 · checked 24 September 2026 · AI-assisted audit

Claim: and the bubble is what stands between the planets and the interstellar medium.

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
A possible direct exposure of the Earth to the cold dense interstellar medium 2–3 Myr agoabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Model
The source reads: the heliosphere shrinks to a scale of 0.22 au, smaller than the Earth’s orbit around the Sun. This would have put the Earth in direct contact with the dense interstellar medium for a period of time
Supports
Where Are Voyager 1 and Voyager 2 Now?Voyager 1 section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Voyager 1 and its twin, Voyager 2, are the only spacecraft to ever operate outside the heliosphere, or the protective bubble of particles and magnetic fields generated by the Sun.
Supports
A possible direct exposure of the Earth to the cold dense interstellar medium 2–3 Myr agomain text, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Model
The source reads: This motion creates a cocoon (astrosphere) that protects planets from the ISM. The Sun’s cocoon is the heliosphere.

What this does not establish

The sources call the bubble protective; they do not say it keeps everything out.

Claim 79 · checked 24 September 2026 · AI-assisted audit

Claim: One simulation finds that if the Sun passed through a cold, dense cloud two to three million years ago, which maps of the galaxy’s hydrogen allow, the bubble shrank inside the Earth’s orbit and left the planet in direct contact with interstellar gas.

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
A possible direct exposure of the Earth to the cold dense interstellar medium 2–3 Myr agoabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Model
The source reads: by modelling the 21 cm data from the HI4PI survey
Supports
A possible direct exposure of the Earth to the cold dense interstellar medium 2–3 Myr agoabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: finding that the Solar System may have passed through the LRCC in the constellation Lynx 2–3 million years ago. Using a state-of-the-art simulation of the heliosphere, we show that during the passage, the heliosphere shrinks to a scale of 0.22 au, smaller than the Earth’s orbit around the Sun.
Supports
A possible direct exposure of the Earth to the cold dense interstellar medium 2–3 Myr agoabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: This would have put the Earth in direct contact with the dense interstellar medium for a period of time
Qualifies
A possible direct exposure of the Earth to the cold dense interstellar medium 2–3 Myr agomain text, third paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Model
The source reads: there is at least a 1.3% chance that the heliosphere encountered the tail of the LRCC 2 million years ago
The authors call this a lower limit: “So, the low chance of collision is a lower limit.”

What this does not establish

A single modelling study. The passage through the cloud is inferred from 21 cm maps, with a chance the authors put at no less than 1.3 per cent; they say geological evidence from iron-60 and plutonium-244 agrees with it.

Corrected

24 September 2026. Previously: “One simulation finds that if the Sun passed through a cold, dense cloud two to three million years ago, as maps of the galaxy’s hydrogen suggest it may have, the bubble shrank inside the Earth’s orbit and left the planet in direct contact with interstellar gas.” Integrity pass: read in full, Opher and others put the chance that the Sun met the cloud at no less than 1.3 per cent, which they call a lower limit. The maps allow the passage; saying they suggest it overstated a probability the authors give as small.

Claim 80 · checked 24 September 2026 · AI-assisted audit

The part nobody has seen

Claim: The part nobody has seen

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
A Sedna-like body with a perihelion of 80 astronomical unitsabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: the as-yet unseen outer Oort cloud, some 10,000 AU from the Sun

What this does not establish

Read as an abstract.

Later work looked for

Claim 81 · checked 24 September 2026 · AI-assisted audit

Whether the Oort cloud is there

Claim: Whether the Oort cloud is there

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

Claim: No object has ever been observed in the outer Oort cloud.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
A Sedna-like body with a perihelion of 80 astronomical unitsabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: the as-yet unseen outer Oort cloud, some 10,000 AU from the Sun
Supports
Oort Cloud: Factsopening
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: a theorized group of icy objects collectively called the Oort Cloud

What this does not establish

Trujillo and Sheppard was read as an abstract. Long-period comets are observed once they have left the cloud and fallen inward.

Later work looked for

Claim 83 · checked 24 September 2026 · AI-assisted audit

Claim: Oort inferred it in 1950 from a score of well-observed original orbits:

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.

Supports
The structure of the cloud of comets surrounding the solar system, and a hypothesis concerning its originpage 91, summary
Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Astronomical observation · Observational study: associations, not causes
The source reads: From a score of well-observed original orbits it is shown that the "new" long-period comets generally come from regions between about 50000 and 150000 A.U. distance. The sun must be surrounded by a general cloud of comets with a radius of this order
Supports
Oort Cloud: Factsopening
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: In 1950, astronomer Jan Oort proposed that some comets come from a vast, extremely distant spherical shell of icy bodies surrounding the solar system.

Claim 84 · checked 24 September 2026 · AI-assisted audit

Claim: the “new” long-period comets, he found, generally come from regions between about fifty thousand and a hundred and fifty thousand astronomical units, so the sun must be surrounded by a general cloud of comets with a radius of that order.

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.

Oort’s own words closely paraphrased; "new" is his term, in his quotation marks, for comets on their first passage near the Sun.

Supports
The structure of the cloud of comets surrounding the solar system, and a hypothesis concerning its originpage 91, summary
Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026 · Astronomical observation · Observational study: associations, not causes
The source reads: From a score of well-observed original orbits it is shown that the "new" long-period comets generally come from regions between about 50000 and 150000 A.U. distance. The sun must be surrounded by a general cloud of comets with a radius of this order

Claim 85 · checked 24 September 2026 · AI-assisted audit

Claim: Nineteen orbits carried the argument: twenty-two had been computed accurately, and three were set aside because their errors were too large.

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.

Supports
The structure of the cloud of comets surrounding the solar system, and a hypothesis concerning its originpage 91, section 1
Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026
The source reads: there are 22 for which ... accurate calculations have been made of the orbits ... excluding 3 for which the mean error of the reciprocal major axis, 1/a, is larger than 0.000100, the values of 1/a for the remaining 19 comets are distributed as shown in Table 1.

Corrected

24 September 2026. Previously: “Nineteen orbits carried the argument, out of the twenty-two that had been computed well enough to use.” Oort says all twenty-two had accurate orbits and three were excluded for their mean errors, so twenty-two were not all good enough to use.

Claim 86 · checked 24 September 2026 · AI-assisted audit

Claim: He took the random distribution of their orbital planes and perihelia, and the preponderance of nearly-parabolic orbits, as consequences of that cloud being stirred by passing stars rather than as signs that the comets came from interstellar space.

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.

Supports
The structure of the cloud of comets surrounding the solar system, and a hypothesis concerning its originpage 91, summary
Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026
The source reads: the random distribution of orbital planes and of perihelia, and the preponderance of nearly-parabolic orbits, may be considered as necessary consequences of the perturbations acting on the comets.
Supports
The structure of the cloud of comets surrounding the solar system, and a hypothesis concerning its originpage 95
Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026
The source reads: has often been taken as an indication that they are of interstellar origin. However, if we take account of the influence of the other stars on the cloud of comets
Supports
The structure of the cloud of comets surrounding the solar system, and a hypothesis concerning its originpage 92
Cited · Link answered, 19 October 2026 · The cited passage was read, 24 September 2026
The source reads: It is evident that they cannot directly come from interstellar space

Claim 87 · checked 24 September 2026 · AI-assisted audit

Claim: Two bodies far beyond the planets, Sedna and 2012 VP113, are read as members of an inner part of it.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
A Sedna-like body with a perihelion of 80 astronomical unitsabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: Here we report the presence of a second Sedna-like object, 2012 VP113, whose perihelion is 80 au. The detection of 2012 VP113 confirms that Sedna is not an isolated object; instead, both bodies may be members of the inner Oort cloud
Supports
A Sedna-like body with a perihelion of 80 astronomical unitsabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: may be part of the putative massive inner Oort cloud

What this does not establish

Read as an abstract. Trujillo and Sheppard say the two "may be" members of a "putative" inner cloud.

Claim 88 · checked 24 September 2026 · AI-assisted audit

Claim: That is a reading of two orbits, not a sighting of the cloud.

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 the abstract’s own "may be" and "putative".

Claim 89 · checked 24 September 2026 · AI-assisted audit

Claim: The inference is strong and the observation is absent.

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.

Sums up the checked claims: Oort’s comet orbits on one side, no sighting of the outer cloud on the other.

Claim 90 · checked 24 September 2026 · AI-assisted audit

Claim: It is one of the largest structures anyone claims is part of the solar system, and it is known entirely by what leaves it.

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.

"What leaves it" is the long-period comets that fall inward and are seen.

Context
Oort Cloud: Factsdistance section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The inner edge of the Oort Cloud, however, is thought to be located between 2,000 and 5,000 AU from the Sun, with the outer edge being located somewhere between 10,000 and 100,000 AU from the Sun.

Claim 91 · checked 24 September 2026 · AI-assisted audit

What was read

Voyager 1 Observes Low-Energy Galactic Cosmic Rays in a Region Depleted of Heliospheric IonsStone and others, Science · PubMed abstract (PMID 23811227), and Science’s editor’s summary carried in the Crossref recordAbstract only, 24 September 2026 · Copyright; quoted briefly
In Situ Observations of Interstellar Plasma with Voyager 1Gurnett and others, Science · PubMed abstract (PMID 24030496), and Science’s editor’s summary carried in the Crossref recordAbstract only, 24 September 2026 · Copyright; quoted briefly
Plasma densities near and beyond the heliopause from the Voyager 1 and 2 plasma wave instrumentsGurnett and Kurth, Nature Astronomy · Abstract and editor’s summary at nature.com; the article is paywalled and has no open copyAbstract only, 24 September 2026 · Copyright; quoted brieflyThe abstract dates Voyager 1’s first interstellar density to 23 October 2013 at 122.6 au. Gurnett and Kurth (2020), read in full, place that first event, 0.055 per cubic centimetre, in October to November 2012, so the year in the 2019 abstract is a slip. The page uses only the distance.
Search for the exit: Voyager 1 at heliosphere’s border with the galaxyKrimigis and others, Science · PubMed abstract (PMID 23811223), and Science’s editor’s summary carried in the Crossref recordAbstract only, 24 September 2026 · Copyright; quoted briefly
Magnetic field observations as Voyager 1 entered the heliosheath depletion regionBurlaga, Ness and Stone, Science · PubMed abstract (PMID 23811226), and Science’s editor’s summary carried in the Crossref recordAbstract only, 24 September 2026 · Copyright; quoted briefly
Cosmic ray measurements from Voyager 2 as it crossed into interstellar spaceStone and others, Nature Astronomy · Abstract and editor’s summary at nature.com; no open copy foundAbstract only, 24 September 2026 · Copyright; quoted briefly
Voyager 2 observations near the heliopauseRichardson and others, Journal of Physics: Conference Series · Journal of Physics: Conference Series 1620, 012016, publisher’s PDF; read in fullRead in full, 24 September 2026 · CC BY 3.0
Magnetized jets driven by the Sun: the structure of the heliosphere revisitedOpher, Drake, Zieger and Gombosi, The Astrophysical Journal Letters · arXiv:1412.7687v2 (26 January 2015); read abstract and sections 1 to 3Read in full, 24 September 2026 · Copyright; quoted briefly
A small and round heliosphere suggested by magnetohydrodynamic modelling of pick-up ionsOpher and others, Nature Astronomy · arXiv:1808.06611, the accepted text under its preprint title "A Predicted Small and Round Heliosphere"; read in fullRead in full, 24 September 2026 · Copyright; quoted briefly
The structure of the cloud of comets surrounding the solar system, and a hypothesis concerning its originOort, Bulletin of the Astronomical Institutes of the Netherlands · ADS scan 1950BAN....11...91O, which has no text layer; pages 91 to 96 rendered as images and readThe cited passage was read, 24 September 2026 · Copyright Astronomical Institutes of the Netherlands; quoted briefly
A Sedna-like body with a perihelion of 80 astronomical unitsTrujillo and Sheppard, Nature · Abstract at nature.com and in PubMed (PMID 24670765); no open copy foundAbstract only, 24 September 2026 · Copyright; quoted briefly
A Foreshock Model for Interstellar Shocks of Solar Origin: Voyager 1 and 2 ObservationsGurnett and Kurth, The Astronomical Journal · The Astronomical Journal 161, publisher’s PDF at iopscience.iop.org, free to read; read in full on 2026-09-24Read in full, 24 September 2026 · © 2020 The American Astronomical Society; quoted briefly
A test for whether or not Voyager 1 has crossed the heliopauseGloeckler and Fisk, Geophysical Research Letters · Abstract in the Crossref record; Wiley and the Deep Blue copy refuse this environmentAbstract only, 24 September 2026 · Copyright; quoted briefly
Where Are Voyager 1 and Voyager 2 Now?NASA Science · science.nasa.gov, as served on the access date; read in fullRead in full, 24 September 2026 · NASA content, not subject to copyright in the United States
Oort Cloud: FactsNASA Science · science.nasa.gov, as served on the access date; read in fullRead in full, 24 September 2026 · NASA content, not subject to copyright in the United States
Lyα Absorption in a “Croissant-like” HeliospherePowell, Opher and others, The Astrophysical Journal · The Astrophysical Journal 961, publisher’s PDF at iopscience.iop.org (open access); read in full on 2026-09-24Read in full, 24 September 2026 · CC BY 4.0
A possible direct exposure of the Earth to the cold dense interstellar medium 2–3 Myr agoOpher, Loeb and Peek, Nature Astronomy · Nature Astronomy 8, 983 to 990; full text from Europe PMC (PMC11335566, open access); read in full on 2026-09-24Read in full, 24 September 2026 · CC BY 4.0