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The Oort Cloud and Close Stellar Encounters

If we assume that the Oort Cloud, that enveloping shroud of comets that surrounds our Solar System and extends to 100,000 AU or beyond, is a common feature of stellar systems, then it’s conceivable that objects are interchanged between the Sun and Alpha Centauri where the two clouds approach each other. That makes for the ‘slow boat to Centauri’ concept I’ve written about before, where travel between the stars essentially mines resources along the way in migrations lasting thousands of years. The resulting society would not be planet-oriented.

When the Dutch astronomer Jan Hendrik Oort deduced the cloud’s existence, he theorized that there was an inner, disk-shaped component as well as an outer, spherical cloud, as shown in the image below. The outer cloud is only loosely bound to the Sun, making the interchange of cometary materials between stars a likely event over the aeons, while gravitational nudges from passing stars can dislodge comets in the other direction as well, causing them to move toward the inner system. Most long-period comets probably come from the Oort Cloud.

Image: Artist’s impression of the Oort cloud. The density has been hugely exaggerated. (c) Pablo Carlos Budassi [CC BY-SA 4.0] via Wikimedia.

I should also mention that we can find the Oort Cloud concept, though obviously not that name, discussed in the work of the Estonian astronomer Ernst Öpik in 1932, which is why you sometimes see the cometary cloud referred to as the Öpik–Oort Cloud. Compared to it, the Kuiper Belt is practically in our backyard at 30 to 50 AU. We’ve pushed probes into the Kuiper Belt, but it’s a matter of pure speculation when we’ll have the technologies to reach the Oort, though of course any future interstellar probes will need to pass through this region. Not to worry, though; comets out here are presumed to be tens of millions of kilometers apart.

At Leiden University in the Netherlands, Simon Portegies Zwart has run simulations mapping the growth of the Oort Cloud that are to be presented in a forthcoming paper in Astronomy & Astrophysics. The work confirms the idea that the Oort is a remnant of the protoplanetary disk from which the Solar System grew some 4.6 billion years ago. While much of it comes from comets ejected from the young Solar System by the gas- and ice-giant planets, the research team suggests that a second population of comets comes from other stars.

Bear in mind that at the Sun’s birth, numerous other stars would have been nearby, from which objects in their circumstellar disks could have been exchanged, along with free-floating debris in the parent star cluster and other interstellar objects. Indeed, a high percentage of the Oort Cloud’s material could have come from such sources, as the paper notes: “About half the inner Oort cloud, between 100 and 104 au, and a quarter of the material in the outer Oort cloud ≳ 104 au could be non-native to the Solar system but was captured from free-floating debris in the cluster or from the circumstellar disk of other stars in the birth cluster.”

Let’s look further into the paper on how mass moves around as the Cloud is formed:

According to Cai et al. (2019) 20–80% (with an average of 50%) of the circumstellar material survives the first 100 Myr of its evolution in the parent cluster. The majority of this mass is lost through encounters with other stars. The amount of material lost from the solar system in the simulation presented here falls in this range, meaning that the circumstellar disk has lost about half its mass due to interactions with other stars in the parent cluster, or about 100 M⊕ to 3000 M⊕. Each of the other processes results in a mass loss of roughly 20%. A small fraction of the ejected asteroids acquire bound orbits in the Oort cloud.

The transport of material from one star to another is seen in the simulations to be “rather symmetric.” While the Solar System is what the authors call “a copious polluter of interstellar space,” so too is it receiving material from other systems. The authors argue that stars in the Sun’s birth cluster would have experienced numerous encounters with other stars, and that the Solar System shows evidence of both single strong encounters and a series of relatively weak encounters, based on the orbital parameters of Sedna and the complexity of the orbits found in the scattered Kuiper Belt beyond 45 AU.

These simulations demonstrate that the Oort Cloud evolved using materials from numerous sources. Here is how lead author Portegies Zwart puts the matter:

“With our new calculations, we show that the Oort cloud arose from a kind of cosmic conspiracy, in which nearby stars, planets and the Milky Way all play their part. Each of the individual processes alone would not be able to explain the Oort cloud. You really need the interplay and the right choreography of all the processes together. And that, by the way, can be explained quite naturally from the Sun’s birth environment. So although the Oort cloud is complicatedly formed, it is probably not unique.”

The paper is Zwart et al., “Oort cloud Ecology II: The chronology of the formation of the Oort cloud,” accepted at Astronomy & Astrophysics (preprint).

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{ 23 comments… add one }
  • Alex Tolley June 4, 2021, 20:22

    If such a large fraction of Oort objects are from another nearby star, then we really don’t need to wait for another high delta-v comet. A random selection of long-period comets should be from another star.

    Low-cost small probes that are fired to do comet intercepts could do sample returns of some by chance would be from another star. This approach requires lots of sampling with small (e.g. CubeSat) very low-cost, sample probes (perhaps just flying through the tail), rather than large, expensive probes.

    • Ron S. June 5, 2021, 8:53

      It’s a delta-v problem. We can get the tiny probe to a comet and even take a sample, but getting it back home requires lots of fuel. So the probe is no longer quite so tiny. Ultimately it may be cheaper and more effective for onboard analysis of samples, and just send back the data.

    • Mike Serfas June 5, 2021, 13:19

      Amateur astronomers should be more excitable knowing that every new comet they discover may be an ancient souvenir from several trips around the galaxy. They should keep an eye out for a comet with warp pods…

  • wdk June 5, 2021, 10:01

    Regarding long period comets and rendezvous to sample for search for matter from other stars, I think that would leave us much in the same position that we are in now – with collection of cosmic dust. Some of it is of extra solar origin, but we don’t know from where.

    A comet with excess velocity or hyperbolic orbit, however, suggests that it is from somewhere specific. We hope we can nail that down and discover significant differences. Send the cubesats in pursuit of those.

    Also, Barnard’s Star with its large proper motion, though it’s close, is “not from around here,” as they would say in New Orleans when you don’t respond correctly to how you want your muffaletta “dressed”.
    But on the other hand, we know that our other neighbors drift closer and farther apart. I don’t expect Alpha Centauri or Procyon to end up at the opposite of the galactic disk in a billion years, but have to wonder how long they are in our vicinity. Could we get significant amounts of debris in our solar system – or they from ours – and could it add up to
    universal biological building block transport. And what would a starter set entail?

  • Neil Stahl June 5, 2021, 17:39

    Surviving by jumping from one Oort object you just digested to the next; depending on being able to find the elements there you need. Sounds like a desperate existence. Then if a lot of last chances pay off some descendants make it to another star system and paradise (assuming no body/thing is there waiting for them).

    There’s a story there for a talented author.

    • gbaikie June 6, 2021, 0:30

      It would be interesting what you would mine between the stars.
      Also what would that environment be like.
      If one traveling thru our asteroid belt, it is just a lot space out there. And between stars, it’s the same story- maybe a bit more space. But it seems a difference is that in Main asteroid belt, most of stuff there is roughly going about the same velocity and roughly in same direction. But get to any of the millions rocks, you have to go in the correct direction. If pass thru, you pass as close a few object which are close as the moon’s distance to Earth. And if big enough your unaided eyes could even see them, maybe and many not. Whereas between the stars and within say 1 year time period, chance “seeing anything” is near zero. But seems if knew wherever thing was, you could go in correct velocity and direction you should find something within a year. But what velocity a direction it going at, relative to you, seems like it doesn’t have the uniformity as objects in Main Asteroid belt would have.
      Or if looking stuff in Main asteroid belt and find something, one might rough idea of where is going when you first find it, and seems objects between stars would have larger difference in velocities and direction.
      Or objects within Main belt will get hit by other objects, and on average there are far less velocity to objects as compared to hitting Earth- and that average is said to be about 20 km/sec second, and least the velocity could be is around the escape velocity of Earth’s gravity well 11 km/sec. Main belt as wild guess could around average 10 km/sec and whatever is greatest gravity well that is “involved” {not much, Ceres is biggest object}. In main belt could hit something at say 5 to 15 km/sec
      How would one characterize the average velocity of all objects travelling between the stars.
      In Oort cloud the answer pretty easily because there a lot objects within Oort cloud- perhaps more 90% of all objects will be Oort cloud objects which have slow velocity- much slower than Main belt objects. But once get far enough away from Oort cloud, one get to point where 1/2 aren’t the Oort cloud objects, and further away, less than 25% are. And how fast are the 75% of objects you could encounter. It seems some could be going faster than 50 km/sec. ie:
      “Because of its high velocity of approach, 110 km (68 miles) per second, Barnard’s star is gradually coming nearer the solar system and by the year 11,800 will reach its closest point in distance—namely, 3.85 light-years”
      Or our Oort cloud objects are slowly moving in regards to us but our solar system is not moving slowly relative to other star system’s Oort cloud objects, and fastest star, seen is going 8% the speed of light,
      If you going fast to or thru many objects going slow there more opportunity to encounter in given time period, and same true if many object moving fast towards you.
      Or if things are traveling faster, you more likely to randomly run across something, but if know “where to go” you can run across a lot more sooner.

  • Peter McKay June 6, 2021, 12:20

    I feel that the scientific community has taken what we have known and found out too much for granted. We need to remind ourselves that like a blind person, we cannot see what we cannot see, and only can use what we can otherwise detect to relate, the best way we can .. THAT WE SHOULD ALWAYS KEEP THIS IN MIND WHEN WE DIVE INTO UNKNOWN SUBJECTS LIKE THIS .. The dark matter or dark energy could very well be a clue to us about this inability ..

    Is there any conjecture that there might be other “periodic table(s)” existing elsewhere ? Is there any scientifically justifiable theory that the periodic table as we know it is the only possible recipe for the universe ?

    • Alex Tolley June 7, 2021, 10:22

      Isn’t the fact that we recognize the terrestrial elements in the spectral absorption lines of stars evidence that the periodic table is universal?

  • Marshall Eubanks June 6, 2021, 13:20

    In our Interstellar Object Taxonomy, these are Type 4 ISOs, Comets captured in the Oort cloud at the formation of solar system. There should be lots of them, and some will appear as long-period comets; the problem will be distinguishing them from “our” Oort cloud objects

    https://arxiv.org/abs/2008.07647

  • wdk June 6, 2021, 18:12

    Several books by or about Freeman Dyson are scattered around the house. In one of them, I had thought I had read his account of nomadic life in the Oort Cloud pushed further and further out. I looked for it in “The Starship and the Canoe” by Kenneth Brouwer, but it seemed to step around that, speaking mostly about George Dyson’s adventures in British Columbia, or else the period when Freeman was focused on Orion, literally blasting around the solar system.

    I suspect that later he must have examined this idea further in another work. Perhaps an account in “Disturbing the Universe”? Even paging through Brouwer’s book, there were some fantastic ideas discussed in both the sense of ingenuity of mind and turning life inside out. And yet at the same time, we have added so many new perspectives in the meantime since the late 1970s.

    Dyson’s interviews in the book emphasize resources available to Orion to head further and further out into space, the basic constituents of moons and Oort Cloud objects. But I think we are discovering as well that solar system resources are abundant once they can be accessed. Some for propulsion, some for settlement – and not necessarily farther and farther out. At this writing the terrestrial planets accessible to us are largely devoid of what would make human life bearable. The moon is a basaltic rock near here and Enceladus is an icy surfaceed body with ocean venting geysers way over there. The Earth itself posed similar problems for stone age people – and yet Egypt of the pharoahs gained access to tin imported all the way from Afghanistan, way off their conceptual map.

    If we were to travel back in time to the mid 19th century to report to authorities what was needed to establish our present day infrastructure that delivers fresh or un-ripe bananas to regions all over where the fruit is not grown, it is enabled not by iron, steam and coal culminating in swift ocean surface steamers, but copper wires, aluminum, alloys of steel, applications of dynamos and reciprocating engines burning petroleum… The aluminum, smeltered in plants with supplies of electric current for heavier than air flight, would be a leap of faith to the technologists of the day. Yet somehow it happened without pre-planning of the sort that time travelers could provide.

    This situation, of course, has feet of clay because it is Faustian
    bargain. But the continued striving got us where we are and – my hope it will continue to be so. Not on account of continuing to tear up the living Earth to gain its resources, but that we can supplement with things long in storage above for now beyond our reach.

    • ljk June 7, 2021, 15:39

      Perhaps you are thinking of this…

      https://en.wikipedia.org/wiki/Colonization_of_trans-Neptunian_objects

      The relevant quote:

      Freeman Dyson has proposed that trans-Neptunian objects, rather than planets, are the major potential habitat of life in space.[citation needed] Several hundred billion to trillion comet-like ice-rich bodies exist outside the orbit of Neptune, in the Kuiper belt and Inner and Outer Oort cloud. These may contain all the ingredients for life (water ice, ammonia, and carbon-rich compounds), including significant amounts of deuterium and helium-3. Since Dyson’s proposal, the number of trans-Neptunian objects known has increased greatly.

      And this video:

      https://www.youtube.com/watch?v=wVGjQSnLg4Y

      • wdk June 8, 2021, 10:50

        On Trans-Neptunian….Thanks!
        I noticed at the site there was this citation:
        Freeman Dyson, “The World, the Flesh, and the Devil”, Third J.D. Bernal Lecture, May 1972, reprinted in Communication with Extraterrestrial Intelligence, Carl Sagan, ed., MIT Press.

        There might have been a recap in some of his other essays, but
        I can’t find them as yet in the books scattered around the house.

  • Tiens van Greuning June 6, 2021, 19:44

    Since I’ve read about the concept on these pages, “slow boating” our way to the stars and out into the galaxy seemed a compelling idea and worthy of further contemplation. Not without some significant challenges that would have to be overcome, but still.

    As far as I can deduce from what I read, our Sun is not part of a local population of stars which all move in more or less the same direction and at a similar speed, but rather it seems to be swimming “up-stream” through a field of local stars. The Alpha Centauri system, if memory serves, is heading to a closest approach of 3.2 light years from us in around 28k years from now.

    If the Alpha Centauri system is part of a population of local stars sharing a similar speed and direction (I don’t know if it is, maybe someone who is more well read can enlighten me?), it seems reasonable that a fair amount of the interstellar visitors coming through our solar system would be coming at us from a certain direction.

    Therefore, if you can hop onto one of these interstellar comets and mine it for resources, once you are far enough away from the Sun’s glare, you should be able to spot other bodies heading in a similar direction with a powerful enough telescope, and once you’ve built some more mining equipment and some more rocket engines, you could hop onto the next one and the next one and in due time, be able to reach any of the stars in the group AC belongs to.

    Also, I suspect that close enough stellar encounters would create populations or packs of comets moving through the field of stars in a different direction, and again if you are far enough from the Sun’s glare, it would be possible to spot some of these rogue packs of comets, and at the cost of somewhat more delta-V, be able to hop onto one of them as well, sending a branch of colonising robots in another direction.

    Of course this all seems very romantic, but there are some serious questions about the feasibility of such an operation.

    My first big question is where is the energy for your mining and manufacturing going to come from. There is no such thing as solar power where you are headed, so it seems you would need to transport a sizeable nuclear power plant with enough fuel to your first comet, and then you must be able to construct a similar power plant and mine enough fissionable material to send to your next comet, and still have enough fissionable material left to fuel your first power plant with for thousands of years.

    Maybe you could construct some large solar powered lasers close to the Sun, and beam energy to the comets you have mining operations on, but who is going to pay for that? I don’t really see a business case for beaming large amounts of energy to some distant comet and getting next to nothing in return. That is, if the laser idea will even work over such large distances.

    It seems there are a lot of technologies that need to be developed before we can attempt something of this nature. But we seem to be headed in the right direction.

    It seems that all the outer space-capable countries have aspirations to set up some sort of permanent human presence on the Moon. There, at least, should be no shortage of stuff to mine, and solar power is there for the taking. You could build swarms of rockets there and launch them anywhere, much cheaper delta-V wise than from Earth. That should really open up the Solar system to us.

    Then there is Elon Musk who seems hell-bent to do more or less the same on Mars. There, too, would be no shortage of stuff to mine, but Solar power is a fraction of what you get on the Moon, so you will have to develop other ways to power your operations.

    Hopefully, once there are some mining and manufacturing operations going on on the Moon and/or Mars, there will be businesses who will start mining some of the near Earth asteroids, developing technologies as they go along, and then we can start venturing into the asteroid belt, where solar power is even less of an option, and then onto some medium to long period comets.

    Maybe 100 years from now we will have matured the technology enough to hop onto an interstallar comet and start to van Neumann the local region?

    • Alex Tolley June 7, 2021, 10:20

      The most likely energy supply for Oort cloud hopping would be from hydrogen fusion, sourcing the hydrogen (and deuterium) from the water and other hydrogen-rich volatiles. If we haven’t mastered fusion by then, I suspect it will have been game over for hi-tech and high-energy-using humanity.

    • wdk June 7, 2021, 11:35

      On the Oort Cloud fuel problem:
      Deuterium is an isotope that becomes depleted in stars and brown dwarfs due to fusion processes. On low mass planets because of its proton and neutron nucleus erodes away into space not as quickly as (proton) hydrogen, so it tends to be a marker of that escape velocity related process. E.g., we presume more deuterium in the atmosphere and waters of Mars than on Earth. And I believe that has held up to investigations on the surface or by orbiters.

      Conventional rocket engines based on nuclear fission or fusion are dwarfed by the task of getting to the nearest stars. Even at that, it depends on what your criteria for transit are: decades? centuries? millenia? But with regard to exploring the Oort Cloud, it is possible to conceive of deuterium fusion rockets being able to replenish themselves at stops at ten kilometer wide Oort Cloud objects. Water ice isotopes and carbohydrate compounds should be pre-solar abundance in their ratios of deuterium.

      As a matter of fact,in the literature the rocket equation delta velocity and mass calculations do not examine such intermediate stop offs frequently if at all. So it’s a toss up of looking around or starting from scratch with some specifics. And at first glance, a difficulty is that to exploit stellar Oort cloud resources, it would be a stop and go type calculation. Accelerate up to a cruise speed and then decelerate down. If you had capabilities to leap tens of thousands of AUs at a time, it might even be worth the trouble, perhaps for artificial intelligence on board. But if you can count on a
      supply of 10 kilometer wide objects of the Ultima Thule variety outside
      of Pluto, I don’t think we are talking tens of thousand of years anymore… And if the missions were planned right, the spacecraft arriving might be bigger than the one that had left the solar system.

      Thinking in these terms though, it brings one back to Enrico Fermi’s
      issue with “Where is everybody?” Here is a way that we could diffuse across the galaxy. if only locally. And it would suggest that if a similar
      species had preceded us they would have examined or attempted the same thing.

      In an entry above, I suggested that moving volatile resources around the solar system would be some of the driver for going to the regions beyond the snow lines of various compounds for sending them to the inner solar system. If that every becomes the case, there just might be
      enough of an economic base for such interstellar traverses. But by then, our other means of exoplanet detection should give us a clearer picture of whether or not there is a reason to set off in the first place. Maybe just for “Bread cast on waters.”

    • Michael Spencer June 7, 2021, 12:29

      Maybe 100 years from now we will have matured the technology enough to hop onto an interstellar comet and start to van Neumann the local region?

      I’ve shared many of your fanciful future predictions myself, over and over; but I always remind myself that the future is hard (to coin a phrase). Remember Ford’s comment that if he’d asked folks what they wanted, they’d ask for a bigger horse?

      So much is unknown.

  • Hal_S June 7, 2021, 7:42

    This raises questions I’ve had for a while: first, if the majority of the Oort cloud was thrown out by gas giants due to ‘Nice model’ planet resonances, then shouldn’t Oort clouds be rare; and only occur around stars that underwent large shifts of gas giant orbits? Do we have any idea how common that actually is?
    Second, doesn’t the Oort cloud suggest that during ‘Nice model’ ejection, there is an odd preference for creating parabolic orbits?
    Elliptical orbits are like long-period comet style orbits where objects return to the inner solar system and cook after a few million years.
    Hyperbolic orbits mean the object leaves the solar system in a few million years. The only way I see to accumulate a large number of objects in orbit at Oort distances would be almost perfect parabolic orbits, i.e. orbits where the object’s speed slows down asymptotically so that it’s basically ‘standing still’ at Oort distances, where the orbit is circularized by passing stars and galactic tides.

  • Hal_S June 7, 2021, 12:06

    This raises questions I’ve had for a while:

    First, if the majority of the Oort cloud was thrown out by gas giants due to ‘Nice model’ planet resonances, then shouldn’t Oort clouds be rare; and only occur around stars that underwent large shifts of gas giant orbits? Do we have any idea how common that actually is?

    Second, doesn’t the Oort cloud suggest that during ‘Nice model’ ejection, there is an odd preference for creating parabolic orbits?

    Outbound elliptical orbits are like long-period comet style orbits where objects return to the inner solar system and cook after a few million years.

    Outbound hyperbolic orbits mean the object leaves the solar system in a few million years. The only way I see to accumulate a large number of objects in orbit at Oort distances would be almost perfect parabolic orbits, i.e. orbits where the object’s speed slows down asymptotically so that it’s basically ‘standing still’ at Oort distances, where the orbit is circularized by passing stars and galactic tides.

  • wdk June 7, 2021, 18:28

    Regarding other star Oort Clouds:
    Posed it as a google search question and came back with a discussion about search of the cosmic background radio and millimeter region.

    https://phys.org/news/2018-08-oort-clouds-stars-visible-cosmic.html

    How deep into the galaxy that might be effective with present day capabilities was debated in the comments – hotly. But for our purposes the local stars would be priority. And even if the Alpha Centauri system is currently devoid of Jovian mass planets, that is not necessarily a disqualifier. In fact, I am not entirely convinced or clear that Oort cloud objects are all thrown out, but chunks of material that formed in the vicinity in the first place. The range or eccentricities nearly 1 for materials thrown out of the solar system does not necessarily explain why so much material would stop and form a hollow sphere around the sun. But then we also have to consider the close approach of other stars. More red dwarfs out there than G2Vs like our sun, of course, but how close do they have to pass before they wreck the whole Oort Cloud
    structure?

  • Michael Fidler June 7, 2021, 21:48

    One way we may be able to tell what has happened in our history is by tracing back the suns close encounter’s with stars from the Gaia data. Maybe even to the degree of when we past thru the star forming regions and the galaxies arms. The dense molecular clouds associated with these areas would have a much higher density of stars, rouge planets and comets. Earth has a history of large impactors, a recent one occurring only 36 million years ago;

    Russia’s Crater of Diamonds.
    https://earthobservatory.nasa.gov/images/148403/russias-crater-of-diamonds

    https://en.wikipedia.org/wiki/Popigai_crater

    https://inside.mines.edu/UserFiles/File/Geology/Popigai.pdf

    We may be able to trace back to find if encounters occurred between our solar system and the star forming regions and the galaxies arms from the Gaia data.

  • Jens Fridthjof Knudsen June 8, 2021, 15:04

    As it looks to me, we need to view the Solar System as a piece of ‘land’. What does it take to settle it? In days past, we would have horse drawn wagons, or maybe nothing else than our legs, or we would use boats, to bring along our families and our belongings when looking for places to live, and we might settle in a place that had arable land, and water, and maybe some forest. Space is different. It has an abundance of ‘space’, and there is abundant sunshine, and large numbers of small (and large) mineable bodies containing the resources needed to build stuff. We need to start out with building something we can inhabit, and use the sunshine for energy, and turn some of the material available into all these things we need, including new land. A ‘farm’, or a ‘village’, only the context is a bit different from what we are used to from where we live today. If we do, and if our communities, whatever sizes they have, keep multiplying in numbers, we have pretty much already cracked the code for the asteroid belt, the Kuiper belt, the Oort cloud, and whatever else we might find further out – as long as there is subtance there that can sustain us, we can stay there. If expansion is leisury, we might not need the insane performance required for a ship going from one star system to the next, because there would be a constantly growing number of places where there would be someone to receive us, and there is the possibility of beamed propulsion both for acceleration effected from the point of departure, and deceleration effected from the point of arrival. It gets easier. What we need to do is to agree on how to build a ‘farm’ – a good one :)

  • Jeff Wright June 9, 2021, 5:08

    Scholtz’s Star passed us long ago…which means anything it perturbed may be only starting to come in now. Could Gliese 710 / DM 61 366 be a smaller object closer in? Betelgeuse was found to be closer and less massive.

    • wdk June 13, 2021, 23:39

      J.W.,
      Thanks for that notice. When I saw a chart a year or two ago, showing nearby stars and where they were headed ( closer or farther away), there was nothing as near in its approach. For anyone who has not followed up on this (e.g., the Wikipedia article on Scholtz’s Star), with the Oort Cloud on order of 100K AUs radius, this binary ( M9.5 and brown dwarf) passed perhaps as close a 50K AU 70,000 years ago.
      Perhaps there were / are additional planetary elements in the system.
      To look at this in another way, a parsec is about 206,000 AUs or 3.26 light years. The close passage was about a quarter of that distance 0r about .815 light years.

      A key question about the passage is with regard to its nature as a sample. If 70,000 years ago there was a passage that close, how long was it since the last, or when will be the next of the same order?
      But even if the frequency is low, or long interval, it happened and must have caused some disturbance. With a brown dwarf as part of its system, why should we not assume other material not present as well: comets, Oort cloud, other planets..?

      The estimates on the age of Scholtz in the summary description were very open ended: 3 to 10 billion years. Wish that it could be pinned down and closer to one extreme or the other. Similar age to the solar system would make its remains nearly indistinguishable from the solar system’s material.

      In addition (sic), with total mass estimated at 0.15 solar, likely the split is something like 0.09 and 0.06 for the two bodies – and they are rotating around their common barycenter. So, with the binary confirmed, I suspect that the disturbance would be increased over the effect of one solitary small star.

      The close approach 70,000 years ago would be the acme of an interval.
      The effects of the approach would begin before that and continue sometime afterwards. Maybe some of our present day high eccentricity interlopers (asteroids or comets with e>1) are associated with this passage.

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