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A Formation Scenario for ‘Oumuamua

The interstellar object we call ‘Oumuamua was bound to be fascinating no matter what it actually was. You discover the first incoming object from interstellar space only once. But this one had its own share of peculiarities. Here was what was assumed to be a comet, but one that showed no outgassing as it reached perihelion and in fact seemed to be unusually dry. Here was an object of an apparently elongated shape, an aspect ratio with which we had nothing to compare in our own system. A tiny but detectable acceleration on the way out of the system seemed to indicate later outgassing, but how was that consistent with earlier data?

I think Harvard’s Avi Loeb was exactly right to point out that among the possible explanations of new objects, we can’t disregard the possibility of a technology from another civilization. That ‘Oumuamua was a natural object is an obvious default position, but we are at a stage in our understanding of the cosmos when we realize that the conditions for life occur elsewhere. We don’t know how often it forms — abiogenesis may be spectacularly rare. But maybe not.

But while we’ll never know with 100 percent certainty what ‘Oumuamua was, we can look forward to many more interstellar objects to evaluate as new instrumentation comes online. Meanwhile, that apparently elongated shape that so distinguished ‘Oumuamua has come under scrutiny from Yun Zhang (National Astronomical Observatories of the Chinese Academy of Sciences) and Douglas N. C. Lin (UC-Santa Cruz), who have run computer simulations that show how it could have formed and go on to explain its other oddball quirks.

“We showed that ‘Oumuamua-like interstellar objects can be produced through extensive tidal fragmentation during close encounters of their parent bodies with their host stars, and then ejected into interstellar space,” says Lin. “Our objective is to come up with a comprehensive scenario, based on well understood physical principles, to piece together all the tantalizing clues.”

Image: This illustration shows the tidal disruption process that can give rise to ‘Oumuamua-like objects. Credit: NAOC/Y. Zhang.

Tidal forces are the key to this work, which is described in a paper in Nature Astronomy. Think Shoemaker-Levy 9, whose spectacular disintegration produced the famous ‘chain of pearls’ as the comet was progressively torn apart by Jupiter’s gravity. In Zhang and Lin’s simulations, the modeling of the structural dynamics of an object passing close to its star produces extremely elongated fragments that are then ejected into deep space. The work shows that aspect ratios even greater than 10 to 1 are not out of the question.

Could such a shape be stable? Evidently so, for the scientists used thermal modeling to show that at tight stellar distances, the surface of such an object would melt and then recondense on its way out of the system, producing a crust that should remain cohesive. We get a ‘shard’ of material being flung into the cosmos in a random direction. Moreover, this is a process that contains within it other unusual aspects of the ‘Oumuamua encounter with our system.

“Heat diffusion during the stellar tidal disruption process also consumes large amounts of volatiles, which not only explains ‘Oumuamua’s surface colors and the absence of visible coma, but also elucidates the inferred dryness of the interstellar population,” Zhang said. “Nevertheless, some high-sublimation-temperature volatiles buried under the surface, like water ice, can remain in a condensed form.”

So we circle back to the fact that ‘Oumuamua showed no cometary activity but an apparent outgassing sufficient to produce a non-gravitational motion, albeit a tiny one. Under the modeling Zhang and Lin performed, the warmth of the approach to perihelion would have activated residual water stores that match the observed trajectory of ‘Oumuamua.

Image: A ‘Oumuamua-like object produced by a simulation of the tidal disruption scenario proposed by Zhang and Lin. Credit: NAOC/Y. Zhang; background: ESO/M. Kornmesser.

We should expect quite a few more interstellar objects in our future. Zhang and Lin believe that on average, a single planetary system should eject a total of about a hundred trillion objects like ‘Oumuamua. The tidal forces in play in these simulations work for any number of source objects, from super-Earths to long-period comets and other material from a debris disk. In other words, there is hardly a shortage of material out of which to form interstellar objects. Doubtless our Sun has spewed its share into nearby interstellar space, shard-like or not.

We’ve had a second interstellar object since ‘Oumuamua, the much more comet-like 2I/Borisov. Whether Zhang and Lin are right in their assessment may eventually become clear as we detect and study further examples. Given their apparent plenitude, we should by virtue of these simulations assume that some, if not many, will share some of the traits of ‘Oumuamua. Eventually we’ll build a catalog that may teach us something about planetary evolution.

The paper is Zhang and Lin, “Tidal fragmentation as the origin of 1I/2017 U1 (‘Oumuamua),” Nature Astronomy 13 April 2020 (abstract).


Comments on this entry are closed.

  • Thomas Goodey April 13, 2020, 14:12

    We will never be able to look at this object Oumauma by any currently conceivable means, for the following reasons:

    (1) The very close-to-sun Oberth maneuver that has been suggested for gaining sufficient speed has never been tried, and developing and perfecting it would take decades and be very expensive indeed. Moreover, it would only be of use for catching up with interstellar visitors, and I don’t think it could be justified.

    (2) For powering such a probe through the long dark trip, a RTG would not be sufficient. A modest and reliable space-rated nuclear reactor would be needed. Such a reactor is not available and not even on the horizon.

    (3) Most important: even if we did manage to send a probe to catch up with Oumauma in, say, 2045, how is it going to find the thing (automatically) when it gets near? I don’t think OU’s trajectory is sufficiently well characterized. This problem has not even been considered.

  • Thomas Hair April 13, 2020, 14:14

    Thank you to Zhang and Lin for showing how straightforward the formation of such an unusual object can come to pass. Many of us having been thinking similar thoughts, but they did the simulation and put pen to paper. Great job! Just wish others hadn’t jumped the shark for the sake of attention. Abiogensis is almost certainly spectacularly rare, otherwise we would not exist. At one percent of the speed of light a billions year old intelligence could traverse the galaxy hundreds of times and found this lovely warm, wet rock over and over and over. We are alone, or they intentionally leave us alone.

    • Richard April 18, 2020, 22:10

      How would you be able to really say that there could be life, what would power another group of lifeforms somewhere else? Until a space probe is sent, or I guess the Webb telescope could perhaps give some clarity in other systems, on possible or past tense, were habitable planets, considering the distance. Nobody can confirm there is any life that is like us that could produce electricity.

  • Gary Wilson April 13, 2020, 17:16

    I like Occam’s razor for this one. Zhang and Lin make a lot of sense here.

  • Laintal April 13, 2020, 17:33

    Thanks Paul

    Another interesting article

  • Mike Serfas April 13, 2020, 18:20

    I can’t disprove that Oumuamua is a space probe, but surely the Moon is a better candidate for that role. It is in a perfect position to watch over us, promote habitable conditions, and serve as a base for observation and intervention… :)

    • Ljk April 14, 2020, 14:05

      And a great place to bury monolithic devices in.

  • Robert Flores April 13, 2020, 18:41

    Does not This imply that some comet like bodies like Oumuamua have a composition that is atypical compared to a standard example.
    Would a comet comprised of H20,N2,CO2,CH4, (and small amounts of pebble sized rocks that dirties it up) hold together if it were to encounter a strong stellar tidal forces, as this paper assumes.
    Does the fact that Oumuamua’s approach to our sun and the result that it held together and had minimal outgassing imply that it is not typical (Borisov object being one example of more typical composition). What compounds would make an objects surface dry and malleable., Organics? Maybe organic compounds have accumulated on Omuamua surface in large quantities giving it some structural support. What organic compounds would behave to constrain outgassing and at the same time, itself be minimally affected by the solar heating on close approach.
    I picture something like an MM candy, you can heat it up slightly
    and will not deform unless it is place at high heat, Or More likely there was heat but the intensity passed quickly(fast approach, and departure)

    • James Jason Wentworth April 15, 2020, 2:11

      I was thinking of a (physically) candy-like crust as well–something with physical properties, if not a color and flavor, like the solidified coating on a candy apple. (An organic crust that is rather like candy in other ways isn’t out of the question, either, although I wouldn’t be tempted to taste it.) Also:

      In a pre-flyby NASA film about the Mariner 4 mission, titled “Eight Months to Mars” (see: https://www.youtube.com/watch?v=hPOmxx9YWSY ), an unusual theory was discussed, and illustrated with charming special effects. Solar ultraviolet light, acting on the carbon dioxide and methane in the Martian atmosphere, could create a literal “snow of table sugar.” The amount of methane in Mars’ atmosphere is much smaller (and transient) than was suspected in 1965, but that chemical reaction is still plausible, even if the amounts of table sugar produced are much smaller. Other objects, containing more organics (including, say, in clathrates containing carbon dioxide and methane) and subjected to greater UV radiation and heat from their stars, could form resilient, rather candy apple-like crusts.

  • Wojciech J April 13, 2020, 21:56

    A very interesting mission concept regarding direct imagining of exo planets using solar lensing was given further funding by Nasa, it is part of NIAC and apparently first time PHASE III was awarded, I don’t believe this was covered by CD yet, a fascinating concept along other proposals raised here before:

  • Alex Tolley April 13, 2020, 22:25

    It is some clever modeling to show that port cloud objects can make a close star approach and through deformation allow the resulting object to be ejected on an escape velocity. It also shows why such objects cannot be found in our own system as the star must be low mass or a white dwarf.

    However, we did see one of these objects, which suggests that they must be relatively common types for such interstellar objects, even if absolute numbers are low. What we would expect is that white dwarfs should be enriched with such objects as only a fraction escape. It would be interesting if there was some technique that would allow us to make those observations.

    • James Jason Wentworth April 15, 2020, 2:31

      Think of it, Alex–white dwarfs could be surrounded by close-in spherical “super asteroid belts” resembling the Oort Cloud–or disc-shaped “mini Kuiper belts,” or both (or even several) of each, containing objects among which many would be highly elongated due to the greater gravity gradient. It would make fast white dwarf flybys dangerous, and it would look like the scene in “2010” where Jupiter was surrounded by a spherical cloud of monoliths, and someone shouted, “They’re eating the whole planet!”

  • Michael Fidler April 14, 2020, 0:03

    Perhaps ‘Oumuamua is an example of alien species sending out objects that contaminate worlds with viruses. The main purpose is to fast track evolution of worlds with a parasite that changes and improves what exist on them. ‘Oumuamua came within 15 million miles of earth on October 15, 2017 and a trail from a plume of viruses could still be passing thru our solar system. This may be why we currently have a pandemic after the earth passed thru this stream of material on October 15, 2019.
    One of the most unusual aspect of ‘Oumuamua was it light curve, almost as if saying look at me and prepare for a pandemic. This may be the reason it is done this way so advanced civilizations can negate the problem before it starts. We are just a bit below that level where something of this magnitude can be stopped.
    I know most of you look at this as purely speculative fiction, but not to long ago we looked at what is going on right now as pure science fiction.

    • Alex Tolley April 14, 2020, 20:20

      The would require the structure of the storage molecule, DNA or RNA, to be teh same as that on Earth, coupled with the same genetic code. There are implications if this was the case.

      • Richard April 18, 2020, 22:13

        True, and a power source, how is a virus going to be sent to our planet, if there was no power resource. I guess alone that the object was simply a funny looking rock, just passing by. Why not? It happens across our galaxy, and beyond.

    • Gary Wilson April 14, 2020, 21:13

      With respect Michael, Covid-19 is a member of a family of coronaviruses which have evolved on Earth over a very long period of time. These are positive-sense single-stranded RNA viruses. Viruses from an object passing through our solar system would not be related (i.e. in RNA sequence) to other viruses of the same type already found here as this one is. If you are actually joking then please disregard this.

    • Thomas Hair April 14, 2020, 23:07

      Paul is a gentleman and I respect his rules for this website. We all need boundaries and his are sacrosanct as far as I am concerned, but you have passed into an anti-intellectual place that I cannot fathom nor condone.

      • Paul Gilster April 15, 2020, 8:26

        In any case, going much further along the virus path surely leads us down what an old professor of mine called ‘a rabbit hole,’ something into which one descends and doesn’t come easily back out of. So let’s get back to the topic and the paper that inspired the original discussion. We’ve already discussed cometary virus scenarios in the comment threads for a number of recent posts.

        • Michael Fidler April 15, 2020, 9:50

          Sorry about the rabbit hole and you are correct, but let me leave this comment:

          Von Neumann machines are self-replicating space probes sent out to multiply and explore the universe.

          Sounds very similar to the point I was making, only not exploring but advancing life on planets to intelligent beings.

    • Robin Datta April 15, 2020, 0:23

      A virus is like a key that will fit a particular biochemical lock and no other. Some viruses, like master keys, will fit a particular range of locks. And what they do after they fit their locks will differ from one lock to another.

      If one wants to make a virus to invade cells in a planet hosted by a member of some star cluster elsewhere in the galaxy, it will necessitate extremely detailed information.

      Is biology there organized in cells? Do the cells have membranes? What is the composition of their membranes? What molecules are embedded in their membranes? Do they have proteins? Are their proteins composed of the same amino acids as our proteins? What mechanisms do they use for heritable genetic transmission? Are nucleotides involved? Are they the same nucleotides as ours? Do they form chains? Do they have the same genetic code that we do?

      One “no” answer will royally screw up the whole thing.

      • Alex Tolley April 15, 2020, 14:08

        This is what I meant by “implications”. If abiogenesis is common, and the details of life determined by chance, then you are absolutely correct. If however, it was shown that interstellar comets contained bacteria and viruses that were similar in some ways to terrestrial ones, that might suggest [directed] panspermia.

        Having said that, we will be increasingly able to connect viral outbreaks to genetically very similar viruses already in our biosphere. To my mind, this pretty much puts the nails in the coffin of their extraterrestrial origin.

        Extraterrestrial life should be very distinct from terrestrial life. Perhaps not as different as “Andromeda Strain” life, but sufficiently different that we can be sure there is no connection to Earth’s life. The gray area is life elsewhere in our solar system that has some similarities to Earth life that would create ambiguity between another genesis and panspermia [from Earth] depending on the similar features.

    • James Jason Wentworth April 15, 2020, 2:22

      Some doctors and astronomers, noting that some epidemics and pandemics not uncommonly had/have no discern-able “patients zero” (in other words, they seemed to break out everywhere–or regionally–all at once), but have coincided with close comet approaches to the Earth, have wondered if the comets might have been the cause. “Being the cause” could range from spreading actual pathogens to spreading molecules or molecular fragments that pre-existing (on Earth) pathogens find nutritious, causing a “population explosion” among them (*if* comets are a factor, I’d wager that the latter is more likely). We just don’t know which–if either–hypothesis has merit, as of yet.

      • Robin Datta April 15, 2020, 12:51

        “Nutritious” to viruses are complete, functioning, living cells of the specific kinds that they can invade. With regard to bacteria and protozoa, many pathogens capable of endemicity and clusters of cases also have a free-living existence in the environment. But when transmission is from person to person directly or through the mediation of a vector, the pathogens will find the person (and the vector) to be “nutritious”.

  • John walker April 14, 2020, 5:10

    I am surprised that you didn’t mention the implications for the panspermia idea. The intense stresses incurred in the rock come with very high temperatures. Should future surveys discover a high prevalance of elongated objects amongst the population of visiting interstellar objects, it will logically indicate a reduced plausibility of lithopanspermia.

  • Spaceman April 14, 2020, 11:21

    Whether or not abiogenesis is “spectacularly rare”, as you put it, may be the most fundamental question in SETI. If we can demonstrate that the origin of life is an extremely improbable event, then the question of intelligent life existing elsewhere in our galaxy will be answered by default—that is, the nearest life of any kind could be beyond the cosmological horizons. If abiogenesis is not too difficult, then the search for intelligent life at least has a chance of finding something perhaps within our own galaxy. Thus, biochemists with a knowledge of information theory might be just as helpful in SETI efforts as radio astronomers, right?

    • Thomas Hair April 14, 2020, 23:17

      If abiogenesis were not spectacularly rare, then we would have already figured it out or be well on our way to figuring it out. Alas, we have no idea, just a hodge podge of theories. Chemistry is the central science and very well understood. We are alone in the Milky Way.

      An amino acid is to a cell like a rivet is to an aircraft carrier.

      • Robin Datta April 15, 2020, 23:33

        There is one non-specification rivet at two points in the blueprint for sicklers. That is enough to cause sickle cell anemia. The rivets in each line in an aircraft carrier are identical. The rivets in proteins are quite varied. One non-specification rivet can cause a protein to misfold. And rivet specifications bring with them to the protein specific electrical charges, reactivities and dimensionality, all critical to the functioning of the protein.

        • Thomas Hair April 16, 2020, 22:57

          Robin, my sincere (really) apology for my too forward opinion on abiogenesis and extant life in the universe. I have been a naysayer on this subject for many years, but I do hope your optimism leads to a better understanding.

          • Alex Tolley April 17, 2020, 11:57

            Without evidence, all opinions are just more educated versions of arguing “how many angels can stand on the head of a pin”.

            I am hopeful that we will get unambiguous biosignatures within a few decades. But it is possible we may not, and that the evidence points to a sterile galaxy except for our planet.
            If the latter, it may support religions that have put humans as having the central place in the universe while also putting a damper on a powerful reason for funded space science. An “astrobiology winter” may occur. OTOH, the former may stimulate our attempts to reach the stars with automated probes to study that life more directly and may stimulate SETI too despite its lack of success to date.

            • Robin Datta April 17, 2020, 20:08

              Biosignatures from a distance promise microbial growth and possibly more. Megastructures at stars, unusual configurations or movement of stars (suggesting Shkadov thrusters), transuranic elements in stars – all could be fair game. Perhaps also Matrioshka brains that choose to broadcast their presence?

              • Thomas Hair April 18, 2020, 0:18

                I am not concerned with where the scientific method may lead us. It is the greatest invention of the human mind and it is all we have. Currently it suggests that speculation on religious reactions to being alone and Matrioshka brains and megastructures are somethings we can apply that greatest invention of the human mind. However, skepticism is the hallmark of that wonderful invention.

  • DCM April 15, 2020, 4:47

    It’s a piece of rock. While the laws of physics determined its shape during whatever circumstance it was formed and forced on its course its resemblance to an artifact has to be coincidence.
    We should prepare some way of reaching and investigating the next bit of interstellar rubble — robotic self-launching craft that’ll send back data at various points in the solar system — but it’s otherwise no big deal.

  • Michael Fidler April 15, 2020, 10:56

    This is probably the most unusual aspect of comet ‘Oumuamua, that it never had a coma or tail. All the comets that have come in from long over thousand years orbits have become active when nearing the sun. Why was there no emissions from this object, nothing like this has ever been observed in all the observations of objects coming in from deep space. The Interstellar Comet 2I/Borisov and the Super comet Atlas have both been falling apart into smaller pieces, eventialy dooming them to obscurity or planetary devastation if they hit like Comet Shoemaker-Levy 9.

    When Comets Break Up, the Fragments Can Be Devastating If They Hit the Earth.


    • Ron S. April 15, 2020, 12:46

      Did you read the article? The referenced study provides a possible answer to that question. And, no, not all interstellar objects are alike so a variety of compositions and behaviors is quite normal.

    • Alex Tolley April 15, 2020, 13:55

      You should probably read the paper to get your explanation.

      For example:

      Planetesimal parent bodies that originated well outside the
      snow line (at a few astronomical units) are likely to have icy/
      rocky composition similar to that of the comets. But, their surfaces
      are intensely heated by their original host stars during the disruptive
      periastron passage. The thermal modelling (Fig. 3 and
      Methods) shows that the melting and re-condensation (at 3 h
      after periastron) of surface silicates lead to the build-up of desiccated
      crusts on the resulting fragments and the transformation
      from cometary to asteroidal exteriors. The enhancement of cohesion
      due to sintering of silicates in the crusts leads to more extreme
      c∕a (≲1∕10) with a ≈ 100 m (Fig. 2b). These results offer a possible
      formation scenario for the reported shape, size and surface features
      of ‘Oumuamua.
      Heat diffusion continues after periastron passage. At 3 m beneath
      fragments’ surfaces, the temperature may reach 28 K (CO’s sublimation
      temperature) at 37,000 d after periastron (at ~100 au), such that
      a substantial fraction of volatiles in an ‘Oumuamua-size fragment
      may be evaporated. The CO depletion provides an explanation not
      only for ‘Oumuamua’s spectroscopic properties8 but also for the
      observationally inferred ‘dryness’ (that is, large rock/ice-ratio compared
      with cometary material) of the interstellar population10,11.
      Despite the CO depletion,…

      • Michael Fidler April 16, 2020, 9:14

        And that happen how many years ago? This seems a little too contrived to fit the facts, ten thousand years in deep space and no ice? Like I said anything coming from that deep freeze is going to have a lot of ice build up over the eons. The simple point is that ‘Oumuamua was not cooked yesterday.

      • Michael Fidler April 16, 2020, 9:32

        Oh, I almost forgot, name one asteroid that orbit takes it close to the sun and flies out of the solar system in a long cometary orbit of a over 50AU. There are none, they are all comets with a coma and tail, you need to read your books on comets, if you have any…

        {behaviors is quite normal} Give me a break! {no, not all interstellar objects are alike} all!!! So how many do you have in your back pocket? No wonder the aliens are not talking to us…

  • Hamilton1 April 16, 2020, 7:55

    Yes this could be a possible answer, but for me doesn’t explain away the statistical rarity inherent in the apparition of ‘Mua. The first interstellar object should have been a normal rock from the outer edge of an Oort cloud, not some exotic shard chiselled by tidal disruption. There are millons more examples of the former than the latter in our Solar System.

    • Adam Crowl April 16, 2020, 16:55

      The scenario they sketch is generic enough for such objects to be widespread. Hardly exotic.

      To everyone,
      On the abiogenesis question, there’s many reasons to think Life is as inevitable as it is to think it’s incredibly hard. Eugen Koonin’s analysis posited a minimal RNA organism that still needed a jump of ~1/10^1080 probability to get started from raw chemistry. He invoked the Eternal Inflation Multiverse to produce it, which would mean we’re alone not just in this Universe, but in a huge Multiverse spread. Of course, as he acknowledged, there might be a simpler path to get that boot-straps itself from basic chemistry, but we just don’t know.

      • Ron S. April 17, 2020, 9:48

        No one believes abiogenesis came about by the spontaneous assembly of a complex molecule. His simplistic analysis demonstrates that! Besides, assemble one molecule and it will spontaneously disassemble because the environment won’t support its existence. Multiverses is an extravagant and unhelpful hypothesis.

        Physics plus time equals abiogenesis.

      • wdk April 17, 2020, 18:44

        Chimpanzees serving for millenia like galley slaves at typewriters in an effort to write Shakespeare sonnets and plays is a statistical metaphor that comes to mind. This line of argument seems to suggest that Shakespeare was an outlying chimp who somehow beat simian based odds.

        It was a few decades ago, I believe, in the New Yorker, in which Stanislaw Lem wrote a series of short stories or essays; and I swear that one of them was an examination of his own ancestry and the circumstances of his own birth. Or someone like him with roots in World War I with the shaking and stirring of the populations that resulted from the event.

        Since the story of his antecedents came down to several chance meetings in field hospitals on the various fronts of the Great War and previous ones, the author looked at the statistical likelihood of his own birth.

        The odds of duplication of circumstances were something of the same order as Koonin’s.

        Yet there he was writing his story. Making it up, perhaps; but something similar must have happened: to his neighbor, the other subscribers reading and to you and me.

        Is this hand waving? Perhaps. Yet it is not only possible, but we experience it – and it is based on the pre-existence of a template or pattern. One that allows individuality and consciousness by statistical analysis is even a higher vault to make than the effort to produce life itself. Especially if it is a one time occurrence. But Leibnitz would be proud: we live in the best of all possible multiverses – unless, of course, there is one that features life and sentience beside us.

        In conclusion, I am inclined to accept both possibilities: that ‘Oumuamua is an extenuated interstellar object – and that something akin to panspermia is possible, perhaps on account of the notion that so much can be done with “code”. Depending on which model is in effect, miles per gallon rating may vary.

      • Alex Tolley April 18, 2020, 13:07

        Do you have a reference to Koonin’s calculation? I ask because it seems like the IDer’s argument against abiogenesis, but Koonin’s work is steeped in evolutionary theory which would suggest he fully understands how an RNA could evolve. [Unless he believes in Behe’s “irreducible complexity”, which seems at odds with his work.]

        30 years ago, Stuart Kauffman showed how the probability of self-ordered metabolisms could theoretically appear with a random set of compounds and we are starting to test that idea with real chemistry. There have been countless computer simulations as well as directed evolution in labs of enzyme catalysts that can be tailored to specific tasks. What we need, I think, is proof that chemistry can make increasingly complex molecules (DNA, RNA, proteins) beyond the basic amino acids and oligopeptides that seems to be easily made under a variety of conditions, starting with the Miller-Urey experiment. Once we have that, we are off to races and the concept of irreducible complexity (and with it a creator) is consigned to the dustbin. It would also support the case for abiogenesis being common on planets than can support the necessary conditions.

  • Mike Serfas April 17, 2020, 22:01

    I don’t want to repeat the same postings, so I’ll just mention that I spoke before regarding the implausibility of extraterrestrial coronavirus at https://www.centauri-dreams.org/2020/03/04/calculating-lifes-possibilities-on-titan/comment-page-1/#comment-202046 and on the idea of some of our biochemistry perhaps resulting somewhat predictably from a planet with hydroxylapatite and formaldehyde at https://www.centauri-dreams.org/2020/02/14/boundary-conditions-for-emergent-complexity-longevity/comment-page-1/#comment-201473

  • wdk April 20, 2020, 21:00

    We have two data points to consider here:
    1. Levy Shoemaker breaking up as it approached Jupiter circa 1995. If Jupiter were a point mass, I suppose the comet would have continued on a high eccentricity path, but I do not know if it would be an exit from the
    solar system ( e >1). Could be?
    2. ‘Oumuamua with excess velocity and a hyperbolic passage not particularly close to any object that would cause tidal disruption, but purportedly consisting of stony material.

    Earlier we had some discussion on this site about the upper layers of white dwarf stars being repositories for crushed terrestrial planets, giving their upper shells an enrichment of planet elements ( increased metallicity in astronomical terms). In this instance, the argument was that white dwarf diameters were small and enrichment from planets would be deep. And that there would be a dissipative mechanism to drag all that material down to the surface.

    Now we’ve got an argument to the opposite effect. Instead of ground up planets of white dwarf rings experiencing dissipating forces, they are providing the flyby mechanism for hurling material into space. This could best be done in a binary system. For the white dwarf, to get to it state, would also tend to clear a lot of planetary debris out of the way, what with red giant phase, etc.

    But in terms of statistics, it seems as though the red dwarf population would be much higher. White dwarfs need a supply of stars more massive than the sun to die down. Could a red dwarf serve in lieu of a white dwarf? The tidal forces and thermal environment would not be as intense, but we don’t really know what ‘Oumuamua is ‘Oumademade of.

  • ljk June 3, 2020, 12:23