Friday, February 12, 2016

Why I believe in Planet Nine.

In my last post I went into detail on ways in which our Planet Nine hypothesis could be wrong, and I suggested for you, if you’d like to be a Planet Nine skeptic, which you’re encouraged to be, what new observations you should be looking for before you start to believe it yourself. Here, I’m going to tell you why I already am a believer in Planet Nine and why maybe you should be too.

As we’ve discussed, the Planet Nine hypothesis was initially developed to explain one simple phenomenon: the alignment of the most distant objects in the Kuiper belt. The existence of that alignment looks pretty compelling, but even when you calculate things like a 0.007% chance that it could happen due to chance you still worry about the fact that there are only 6 objects that you’re talking about. Still, Konstantin and I worked on this for about a year until, by about late last summer, we had a nice comprehensive theory which could explain how a massive planet on an elongated orbit could capture equally orbitally-elongated Kuiper belt objects into protected mean-motion resonances. It was a fun result with some cute physics to it, as no one had really considered the effect of such extreme planetary eccentricities on populations of small objects before. It’s always a good day when you learn something new about the ways in which planetary physics can work.
The whole point of Planet Nine was to explain the orbital alignment of these six objects. The number of other phenomena that Planet Nine also explains -- essentially by accident -- is astonishing.

A particularly satisfying aspect of the hypothesis was that it neatly and eloquently explained the peculiar orbit of Sedna.  I have written elsewhere on what is peculiar about Sedna’s orbit and why it demands an explanation, and I have spent 12 years searching for solutions to Sedna’s peculiar orbit, and here was an explanation where we hadn’t even been looking for one. In short, Sedna is peculiar because it has been pulled away from the Kuiper belt by something. And to be pulled away from the Kuiper belt there needs to be something beyond the Kuiper belt to do the pulling. Back when we discovered Sedna, we proposed that perhaps that something was a planet! Or a passing star! Or the cluster of stars that the sun was born in! We didn’t really know. With only a single object there were more possibilities than answers. But as we continued surveying the outer solar system and found no new bright planets out there, we gradually settled into the view point that the most likely explanation was that Sedna had been pulled away from the Kuiper belt by the combined effect of the nearby stars that formed along with the Sun 4.5 billion years ago. This proposition was exciting: Sedna would be a fossil record of the birth of the Sun itself, and finding more of them which teach us about that time period.

Now, however, we have a simpler explanation. If a planet is forcing the most distant objects into alignment, it will also take these most distant objects and periodically pull them away from the Kuiper belt before pushing them back in. In fact, the Planet Nine hypothesis demands that objects like Sedna, and also 2012 VP113, a more recently discovered by similarly odd object, exist. After 12 years of searching for the explanation for Sedna we found it by trying to explain something else entirely.  

Interesting side note: As I was writing this post I noticed something that I hadn’t before. It’s not just Sedna and 2012 VP113: all of the distant objects which are pulled even a little bit away from the Kuiper are in our cluster (specifically, if you look at all objects with semimajor axis>100 AU and perihelion > 42 AU).  Wow. 

That’s not bad. As a scientist, you would love to form a hypothesis that makes predictions that turn out to be true. That makes you begin to believe in your hypothesis. In this case, we didn’t predict the existence of Sedna and then go find it, but rather we knew about Sedna and accidentally came up with a solution. That’s more of a two-birds-with-one-stone situation than a prediction, I think. Still, we were quite pleased.  While previous speculation about planets beyond Neptune had struggled to find viable explanations for even single phenomena, we had come up with a relatively rigorous theory which naturally explained two seemingly unrelated phenomena.

At this point I think that Konstantin and I were mentally ready to publish a paper with a conclusion something like “here’s a nice theory which explains two different things and hey it’s even quite plausible!”

What happened next is what made me go from finding the explanation plausible to finding the explanation likely. While sitting in my office looking at the outputs of our gravitationally simulations, Konstantin and I realized that Planet Nine had another major effect that we hadn’t anticipated. Some of the objects with very distant elongated orbits had their orbits twisted so that instead of being more or less oriented along with the disk of the rest of the solar system, they were essentially perpendicular to it. And, when they happened, instead of being lined up with the other distant objects, their orbits swung off to the left or to the right by nearly 90 degrees. I described these orbits as “wings” because that’s how they looked in the simulations.

Objects with perpendicular orbits? I remember when one was discovered a few years ago. It was so unusual that it was nicknamed “Drac,” in honor of Dracula’s ability to climb on walls. Or something like that. I was quite excited to quickly look up the orbital parameters of Drac and see if its orbit corresponded to the location of the wings, but, to my chagrin, Drac was the wrong sort of object. I had remembered correctly that Drac was perpendicular, but its orbit did not go nearly far enough from the sun to be affected by Planet Nine. And it was not even pointing in the right direction. The origin of Drac was still a mystery, but it didn’t seem connected to Planet Nine (oh but it is; more later!).

While Konstantin and I were still sitting in my office, disappointed by Drac, I thought to look at the complete database of all of the object discovered in the outer solar system, and, to my surprise, there was a collection of objects that were not part of the Kuiper belt that we had overlooked. These were object which, though though were quite elongated and went to great distances, traveled far inside the orbit of Neptune – coming nearly to the orbit of Jupiter in some cases – before swinging back out to the distant reaches of Planet Nine. We had ignored these objects previously because we knew that when objects came into the giant planet region their orbits would be modified by interactions with the planets. What we hadn’t anticipated is that objects coming in on perpendicular orbits would have much less of a chance to have their orbits modified. Our simulations showed that objects with distant elongated perpendicular orbits which came close to the giant planets still maintain their alignment to the wings.

When we realized this, Konstantin stay riveted in his chair in my office while I plotted the locations of these objects which we had overlooked. There are 5 of them. I told him, “If these are right where we predict they should be my head is going to explode.” I plotted them. Four are on one of the wings, the fifth is on the other wing. Right as predicted. My head did not actually explode, I think, but it is possible that my jaw hit the floor. We were both silent for a minute, and Konstantin said, in a semi-amazed voice, “This is actually real, isn’t it?”
The distant objects with orbits perpendicular to the solar system were predicted by the Planet Nine hypothesis. And then found 5 minutes later.

Yeah. I think it’s real. As Konstantin later said, “It’s like killing two birds with one stone and not even realizing there was a third in the tree and killing it, too.” The existence of the elongated perpendicular Centaurs – as those objects are called – was a pure prediction that was dramatically confirmed. Sadly, the rest of the world didn’t get to participate in the drama, as it all took place over the course of about five minutes in my office last fall, but trust me on this one: the drama was there.

And Drac, which had been such a disappointment? Once we started looking we realized that our gravitational simulations create Drac, too. Sometimes, when the elongated perpendicular Centaurs do get too close to giant planet, that planet pulls their orbit a little close, and also swings the orbit around randomly. Another Drac is born. The Planet Nine hypothesis requires the existence of objects with orbits like Drac, which otherwise had no plausible explanation.

Does that make four (five?) birds yet? Hard to keep count.

Here, then, is the summary of my reactions to each of the four (now five) things explained by Planet Nine
  1. A distant massive eccentric planet can capture eccentric Kuiper belt objects into elongated anti-aligned orbits like the ones we see: Hey, that’s cool!
  2. The Planet Nine hypothesis explains Sedna, and requires Sedna to exist: Wow. That’s a really nice hypothesis that sounds pretty plausible!
  3.  The existence of Planet Nine predicts the existence of elongated distant perpendicular Centaurs in specific locations and they are then found to exist. Holy cow. Planet Nine is real!?!?!
  4. The Planet Nine hypothesis explains the unusual orbit of Drac and requires that objects with orbits like that will exist: Of course it does.
  5. The Planet Nine hypothesis explains why all of the distant objects which have been pulled away from the Kuiper belt are equally clustered: Any vestigial doubts have vanished.
 At this point my main question is “what unusual phenomenon in the Kuiper belt does Planet Nine not explain?” (We have, regretfully, come to the conclusion that Planet Nine cannot account for the parting of the Red Sea or the waning of the ice ages, though both of those possibilities have been suggested to us multiple times).

So I believe. But it’s OK if you’re not ready to believe. Unlike some hypotheses, this one has a definite proof. We have to go find it. We will. I have very little doubt that we will.

63 comments:

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    1. Maybe? Maybe not? We haven't figured out why, but I'd say there is a 20% we will suddenly realize that it does.

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    2. Could a O.1 earth mass object in the thrall of planet nine account for it? one that goes say 60ish AU at perehelion. Under the current definition it would be a dwarf planet...

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    3. people have tried similar ideas for a decade now, with limited success.

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    4. Mike, what if you had the ultimate absurd scenario whereby Neptune and P9 were in some kind of resonant orbital "tag-team" situation (like Jupiter and Saturn)? What would have to happen for the two planets to be jointly responsible for the Kuiper Cliff anomaly?

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    5. hmmmmm. i don't see it. but that doesn't mean it can't happen.

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    6. "Neptune and P9 were in some kind of resonant orbital "tag-team" situation (like Jupiter and Saturn)?"

      Like how Jupiter and Saturn moving farther apart caused resonances to sweep through the inner solar system?

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    7. Assuming it's not entirely out of the realm of possibility, would it help or hurt the possibility of an orbital resonance situation, given Neptune's current location in its orbit, if P9 were currently located in the "blinding light" of the Milky Way in its orbit, especially since you've already eliminated vast sections of the night sky by virtue of the various night-sky surveys you've searched?

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  2. Does this mean the next paper is ready?

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    1. but after noticing the perihelion effect yesterday I have spent all day looking at that, instead of finishing. sigh.

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  3. Mike, thank you for sharing all of the fascinating technical subtleties behind this awesome prediction with the non-scientist laymen such as myself! I look forward to each and every new posting of yours with bated breath as they say! Now where has that dang Planet Nine gone to, huh!

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  4. "Now I'm a believer.
    Not a trace
    Of doubt in my mind."

    http://youtu.be/XfuBREMXxts

    BTW:For "objects with orbits like that will exit", read, "objects with orbits like that will exist".

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  5. This is all very impressive. Hopefully you don't have to wait as long as Einstein when he predicted gravity waves!

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  7. Typo I noticed: "recently discovered by similarly odd object"

    You lost your "but" there. =)

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  8. Over the long term, this looks very like a process of evaporation and condensation of KBOs, from and to their condensed phase in the general population, induced by Planet Nine. Is this an accurate way of looking at the dynamics?

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  9. Does the wider gravitational environment of passing stars still have a role in maintaining the KBO population in this model?

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  10. Does this model change our view of how the more general features of the KBO spectrum arise and are maintained? I'm thinking of the role of the outer planets in this process.

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  11. Does this model have any obvious implications for our theories about the early history of the solar system?

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    1. Maybe? If PN was ejected and settled into orbit early on before the Sun had left our birth cluster, it sets the ground for an early JS resonance.

      [I have put a comment in an earlier thread on how the latter could alleviate the tension with the existing, but scant, geological and biological record of early Earth.

      Early zircons (> 3.5 Ga) don't show any impact stress fractures. And there are putative fossils older than 4.1 Ga now. Though It can take from years to never to ascertain their biological origin, need more material and context both.

      In both cases it is hard to see where any putative massive ocean evaporators fits in, something that current Nice models (well, maybe not Nice 2.0) can suggest.

      Oh, there are alternatives, there always is in such open questions. But the more likely explanation could be that the JS resonance happened before the Moon formed.]

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  12. Are you taking any medication to prevent your head exploding?

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  13. Random connections….

    Comet orbits? Kreutz family heads in from the direction of Canis Major which isn't very far from the aphelion of P9.

    I recall some animations of populations of asteroids stirred up by Jupiter into weird resonances… See https://www.youtube.com/watch?v=yt1qPCiOq-8 Room for a similar affect for P9?

    Pioneer 10 is headed in the Orion/Taurus region but they lost the signal in 2003 and it's only some 80 AU out. It'll take a very long time to get out to 1200AU.. but then when would it start to feel and affect and the signal would be far weaker then…. but is it worth it for someone to figure out how to recover the signal?

    The Orion/Taurus direction is also the direction of the tail of the heliosphere. Most of the time P9 would be entirely beyond the solar wind but maybe it would pick up some activity if some turbulent mix of ISM and the solar wind were to cross it.


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    1. "a grouping of comets" is mentioned at https://www.youtube.com/watch?v=ZJscxTyI__s

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  14. a grouping called Damoclids.... http://arxiv.org/pdf/1204.5408.pdf

    "The Damocloids are a group of unusual asteroids, recently enrolling a new member of 2010 EJ104. The dynamical evolution for the Damocloids may uncover a connection passage from the Main Belt, the Kuiper Belt and the scattered disk beyond. According to our simulations, two regions may be considered as possible origin of the Damocloids: the scattered disk, or a part of Oort cloud which will be perturbed to a tran- sient region locating between 700 AU and 1000 AU.…"

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    1. interesting, right? our current simulations can't yet capture that behavior, so we haven't speculated. but interesting. definitely interesting.

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    2. If backtracked comets spend a significant time in that region perhaps this is telling us why P9 would end up there.

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    3. So you are saying a Damocloid sword is hanging over the throne of the Eight Planets model!?

      Like Damocles, I will now excuse myself and leave ...

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    4. Two more thoughts…

      Does the class of objects like https://en.wikipedia.org/wiki/(308933)_2006_SQ372 fit in as another set??

      And does the new paper get around the bootstrap issue? I mean if Sedna is remarkable for being out there where no known planet could kick it but P9 could pull it there, how did P9 get there?

      Work over at http://planetplanet.net/2016/02/04/planet-nine-solar-system-renegade/ seems to revive the work of suggesting Sedna was itself captured.

      And love the question/thoughts on the setting beyond the heliospehere I found at https://www.youtube.com/watch?v=1jPxZQoVVZo (you'll see I pointed to this general question above a few comments.)

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  15. There would have to be some effect on the Oort cloud, no?

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    1. probably not, really. the oort cloud is even further, still.

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    2. probably not, really. the oort cloud is even further, still.

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  16. "all of the distant objects which are pulled even a little bit away from the Kuiper are in our cluster (specifically, if you look at all objects with semimajor axis>100 AU and perihelion > 42 AU). Wow. "

    A search using those parameters gives me five objects, all with a>200.

    Is the absence of q>42 among the objects with 100<a<200 significant? Should the mechanism proposed for raising the perihelion of 2004 XR190 work in this range?

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    1. it is hugely significant. i've been working on it for 2 days now....

      I think 2004 XR190 is a completely different mechanism, though.

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    2. The objects with q > 42 should extend farther out then, past a = 200, and these are missing?

      Is it just the high perihelion objects that are missing beyond a = 100 or is there a shortage of lower perihelion objects too?

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  17. Could p9 also account for other oddities? Uranus' rotation, Pluto's inclination, Triton, etc? A scenario where p9 careened thru the neighborhood headed to it's current orbit?

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    1. Pluto's inclination is simply due to Neptune's perturbation. Triton seems explainable as a captured formerly binary KBO. Uranus I'm less certain about. But, overall, much of the solar system seems explainable just with the local planets. It's the weird ones that have no other obvious explanation that we're interested. The tilt of the sun with respect to the eight planets? Definitely could be caused by Planet Nine (though there are other explanations), for example.

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  18. Would P9 cause a clustering of inclinations for objects with aphelia just inside its perihelion?

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  19. we don't see that in our calculations.

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    1. Would it cause a sharp step down in the number of objects with aphelia greater than its perihelion?

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    2. Perhaps the clustering of inclinations only shows up when Neptune is migrating.

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    3. Looking at this again its not clustering, its just missing low inclination scattered objects. And not related to Planet Nine.

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  20. "As I was writing this post I noticed something that I hadn’t before. It’s not just Sedna and 2012 VP113: all of the distant objects which are pulled even a little bit away from the Kuiper are in our cluster (specifically, if you look at all objects with semimajor axis>100 AU and perihelion > 42 AU). Wow."

    Yes, wow! I was wondering about that from the (on this point scrappy) illustrations hinting at all having a perihelion outside the main Kuiper belt. But since it wasn't mentioned I assumed there were exceptions and didn't ask.

    First rule of questions: never assume.

    So you just know I now have a question. =D I do hope someone tries to estimate the current uncertainty of PN testing?

    It was ~ 5 sigma by my back-of-the-envelope uninformed guesstimates before. Now I think it may indeed be passing into 7 sigma territory of the extraordinary evidence needed for an extraordinary claim: " Any vestigial doubts have vanished."

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    1. Oh, I guess the first rule of question rather is: stop assuming.

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    3. I don't know; when you start to say something like "5 sigma" or "7 sigma" you are speaking in a very specific statistical manner with a very specific statistical meaning. I think there is no way to calculate meaningful statistics for much of the Planet Nine predictions in a sufficiently rigorous way to give sigma any meaning.

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  21. This article ( http://arxiv.org/abs/1303.3098 ) shows a possible conflict in the ratios of scattered disk objects and Oort cloud objects determined by formation models and estimates from observations.

    Could Planet Nine have removed enough objects from the scattered disk to resolve this?

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  22. Do your simulations provide any insight as to what general range of conditions would have caused planet nine to be ejected entirely from the solar system rather than entering its current predicted orbit?

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  23. Wow, the way you describe both of your efforts and dawning realizations with each additional piece of the puzzle bolstering the prediction, is palpable, thankyou for sharing the time to take us all through it. Good-hunting.

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  24. What a pleasure of a blog to read on my 70th birthday. I keep hoping for as many discoveries like this in my lifetime, of course tops on the list, evidence of life outside of Earth. Your blog is so well written for the general reader, it is a great contribution to the spread of knowledge, which is so important, and becoming so sadly neglected in our society. Thanks for your contributions.

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  25. Mike, FWIW, I think the comments in your blog are broken. As I hit preview, it went to a page to confirm the Google+ identity I was logged it, which I confirmed, but when it came back to Preview, it reverted to "Unknown". Glancing back thru comments, I see all unknowns, except for your posts. Ergo, using not even the advanced math you use in your work, but my intuitive computer programming and web design troubleshooting skills from 35 years work, I suspect your comments implementation needs investigation. Just saying there is a good chance.

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    1. And, this time, instead of previewing, I just hit publish link, and this time it displayed my Google+ identity. Hmmm. There is some eccentric orbit in your bog design.

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  26. If I remember correctly, the blog is Blogger, a web service owned by Google. There's nothing the owner can do about how the software works. Might try clearing your browser cache. You could have some bad cookies. That's usually the reason when Google's identity scheme gets weird.

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  27. Is there any orbital distance from the sun where a Pluto-mass object (made of rock and not ice to keep the sun from "melting" the object) could clear the neighborhood of its orbit? How much closer could this hypothetical object get to the sun than Mercury before its Roche limit would be reached and the object shatters completely? Maybe the second requirement for a planet should state that a planet has either cleared its orbit (or is dynamically dominant) OR has a mass that could be gravitationally dominant around its parent star (regardless of where the object is currently located): a planet has a "dominant mass"?

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    1. See the plot from Margot's paper in "Is Planet Nine a Planet"

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  28. 6. Provides a better fit for observed planetary orbits? http://arxiv.org/abs/1602.06116v3

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  29. 2006 SQ372 Is a centaur with an perihelion of 24au and an aphelion of 1570au. It has a argument of perihelion of 122° so it should also be affected by planet nine, it's to far from Uranus or Neptune. Tell me if I'm wrong!

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  30. 2006 SQ372 Is a centaur with an perihelion of 24au and an aphelion of 1570au. It has a argument of perihelion of 122° so it should also be affected by planet nine, it's to far from Uranus or Neptune. Tell me if I'm wrong!

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  31. Great work. Of course, math is all you need. But doesn't that make Sitchin's work also cool? The waxing and waning of ice ages is caused by the changing eccentric orbit of the earth. That's also an outcome of math.

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  32. Planet 9 can't be rosponsible for global flood or for parting of Red Sea,....it is true only partly. If more distant Planet 10- I call it Nemesis has prolongated though not too eccentric orbit,..it don't visit indoor, outdor planets, or Kuiper belt,..but 10 can havr influence on period,.. of Planet 9-I call it Nibiru with much more eccentric orbit, which can especially during Nemesis aphelia, perihelia go closer even to indoor planets,.. ?! Pavel Smutny

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