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Weird Orbits of Distant Objects Can Be Explained Without Invoking a 'Planet Nine' (space.com)

Posted by BeauHD on from the uncertainty-of-science dept.

schwit1 shares a report from Space.com: The weirdly clustered orbits of some far-flung bodies in our solar system can be explained without invoking a big, undiscovered "Planet Nine," a new study suggests. The shepherding gravitational pull could come from many fellow trans-Neptunian objects (TNOs) rather than a single massive world, according to the research. "If you remove Planet Nine from the model, and instead allow for lots of small objects scattered across a wide area, collective attractions between those objects could just as easily account for the eccentric orbits we see in some TNOs," study lead author Antranik Sefilian, a doctoral student in the Department of Applied Mathematics and Theoretical Physics at Cambridge University in England, said in a statement.

The duo's modeling work suggests that the strength-in-numbers explanation does indeed work -- if the mass of the Kuiper Belt, the ring of bodies beyond Neptune, is a few to 10 times that of Earth. This is a pretty big "if," given that most estimates peg the Kuiper Belt's mass at less than 10 percent that of Earth (and one recent study put the figure at 0.02 Earth masses). But other solar systems are known to harbor massive disks of material in their outer reaches, Sefilian and Touma noted. And our failure to spot one around our own sun doesn't mean it doesn't exist, they stressed. The new study has been accepted for publication in the Astronomical Journal.

32 of 61 comments (clear)

  1. Planet Nine? by Anonymous Coward · · Score: 3, Insightful

    But we already know where Pluto is!

    1. Re:Planet Nine? by stealth_finger · · Score: 1

      https://youtu.be/GS4Nzwo3cKc

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    2. Re:Planet Nine? by Immerman · · Score: 1

      Except if Pluto is a planet, we should probably count at least Ceres as well, making Pluto #10, and requiring all the gas giants to be renumbered.

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  2. Re: Of course it can! by Sique · · Score: 3, Informative

    Not exactly. The whole mass of the Kuiper Belt (containing millions of objects) has to be about 10 mass of the Earth in this model to explain the special orbits of some known Kuiper Belt objects. But no single object has to be exceptionally large. A million objects each 10 km in diameter would have the same mass than one planet of 1000 km diameter of the same density.

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    .sig: Sique *sigh*
  3. Wait, are you trying to say... by ocsibrm · · Score: 1, Funny

    That Planet X, Nibiru, *doesn't* exist? Well where are the lizard people coming from if not there? Check and mate.

    1. Re:Wait, are you trying to say... by stealth_finger · · Score: 1

      What are you talking about? They are coming from inside the hollow earth, or moon, I forget which, whatever, illuminati.

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    2. Re:Wait, are you trying to say... by jellomizer · · Score: 1

      No it is Mondas, If you look at it with a telescope it will be the earth, but upside down. Because it is so far away from the sun, all the life forms have put their body into cybernetic suites, to survive. And large high powered flashlights on their heads use to vaporize what gets in their way... On earth it would just kill someone.

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  4. Re: Of course it can! by h33t+l4x0r · · Score: 1

    Not exactly. The whole mass of the Kuiper Belt (containing millions of objects) has to be about 10 mass of the Earth in this model to explain the special orbits of some known Kuiper Belt objects. But no single object has to be exceptionally large. A million objects each 10 km in diameter would have the same mass than one planet of 1000 km diameter of the same density.

    Ah, but would the gravitons emitted from such objects warp spacetime similarly? I think not.

  5. Re: Of course it can! by Sique · · Score: 1

    On the other hand, the gravitons would be Spring green. Don't believe it? Just go out there in the Kuiper Belt, sit on a 10 km icy rock, and take a picture of the emitted gravitons: Spring galore!

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    .sig: Sique *sigh*
  6. Re: Of course it can! by h33t+l4x0r · · Score: 2

    The best one could do is take a picture of said green gravitons from the perpendicular, in which case the red shift would turn them brown.

  7. Re: Of course it can! by Sique · · Score: 1

    That always happens if Spring in the Kuiper belt is over, and after Summer, there comes Autumn.

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    .sig: Sique *sigh*
  8. Nothing Has Been Disproven Actually by dryriver · · Score: 3, Insightful

    The news in 2018 was all "There's a Planet X, there's a Planet X". Fast forward to January 21 2019. Two Cambridge PhD's claim "it may be a ring of smaller" objects. Now the news is all "There is no Planet X, there is not Planet X." Nobody has been able to observe either a 9th Planet or a ring of smaller objects yet. So basically, nobody knows whether there is a 9th Planet out there or not. Everybody's speculating. (Btw, Nibiru sounds like a Linux distro =)

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    1. Re:Nothing Has Been Disproven Actually by Freischutz · · Score: 3, Informative

      The news in 2018 was all "There's a Planet X, there's a Planet X". Fast forward to January 21 2019. Two Cambridge PhD's claim "it may be a ring of smaller" objects. Now the news is all "There is no Planet X, there is not Planet X." Nobody has been able to observe either a 9th Planet or a ring of smaller objects yet. So basically, nobody knows whether there is a 9th Planet out there or not. Everybody's speculating. (Btw, Nibiru sounds like a Linux distro =)

      No, the news used to be that a Planet X about 10 times the mass of Earth could explain the strange orbits of some of these Trans Neptunian Objects. Now the news is that a ring of smaller objects could also explain the strange orbits of these same TNOs. It just gives scientists something else to look for. That is how science works, people come up with educated guesses (hypotheses) to explain a phenomenon and then try to confirm or disprove them through observation and experiment. This is just science working properly, so no need to get your underwear all tied up into a knot over it.

    2. Re:Nothing Has Been Disproven Actually by Sique · · Score: 1
      The news in 2018 was: "We can explain the weird orbits of some known Kuiper Belt objects if we assume a planet ten times the size of the Earth."

      And the news now is: "We can explain the weird orbits of some known Kuiper Belt objects if we assume that all the Kuiper Belt objects taken together have ten times the mass of the Earth."

      Nowhere was the news of any existance or non-existance of a Planet X.

      And maybe the news in 2024 will be: "We found a mathematical model of the dynamics of the Kuiper Belt that explains the weird orbits of some known Kuiper Belt objects without assuming more mass or more large objects than our current observations suggest."

      --
      .sig: Sique *sigh*
    3. Re:Nothing Has Been Disproven Actually by dryriver · · Score: 1

      Except of course that a lot of mainstream news outlets reported Cambridge University's latest speculation as "Plant X Debunked" or "There is no 9th planet" or "There never was a Planet X". So a THEORY that there may not be a 9th planet has been reported as FACT that there is in fact no Planet X at all. Is this science? Plugging a few numbers into a mathematical model at Cambridge, immediately talking to journalists about it, and then making millions of average people open a newspaper and think - possibly erroneously - that "there probably is no 9th planet at all"? I used to take Cambridge somewhat seriously. Now I'm not so sure whether the folks over there deserve their stellar reputation. You have a theory. You have no hard proof. And your utterances to the media get reported not as SPECULATION but as FACT.

      --
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    4. Re:Nothing Has Been Disproven Actually by Sique · · Score: 1

      "there probably is no 9th planet at all"

      That's exactly the result we are talking about. Apparently, we don't need to assume a 9th planet to explain what we know right now.

      And until new discoveries and measurements pop up, that will be what we know so far.

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      .sig: Sique *sigh*
    5. Re:Nothing Has Been Disproven Actually by dryriver · · Score: 1

      So you don't KNOW with any certainty that this new alternative theory is any better than the OLD theory. But its good science for dozens of newspapers to write "Planet X Debunked - there never was a Planet X!"??? WTF kind of science is that? What if an actual 9th planet DOES turn out to exist, rather than a ring of smaller objects?

      --
      Why did the chicken cross the road? Because Elon Musk put an AI chip in its head.
    6. Re:Nothing Has Been Disproven Actually by Sique · · Score: 1
      Newspapers aren't Science. Newspapers are newspapers. And they don't report Science is it is, they report about Science or whatever the journalist (who is no specialist in the topic) understood.

      So yes, there are sensationalist headlines. That doesn't invalidate the Science the newspapers are writing about. It might invalidate the way it was reported by people who weren't involved in the original research. If you are interested, most newspapers are referring to the publications they got their information from. And even if those publications in turn weren't the original research, they will be referring to it.

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      .sig: Sique *sigh*
    7. Re:Nothing Has Been Disproven Actually by drinkypoo · · Score: 1

      No, the news used to be that a Planet X about 10 times the mass of Earth could explain the strange orbits of some of these Trans Neptunian Objects.

      Yes, but that was an idiotic idea because we could actually find it if it were that large. And it was an idiotic idea to report that idiotic idea, because it led to the surge of dipshits who believe in Nibiru, etc. The same guy I can't just avoid has told me three times now about how this planet is actually passing through Earth's orbit, how NASA has orbited a "sun simulator" that hides the actual sun, blah blah fucking blah. And you tell him that even amateur astronomers would notice the effects that would have on our solar system and he doubles down on crazy. People like that have been spurred on by this kind of unfounded horse shit.

      Now the news is that a ring of smaller objects could also explain the strange orbits of these same TNOs.

      Yeah, and unlike something larger than Earth, we would actually have trouble finding those smaller objects. That makes it a plausible theory which passes a basic sniff test, unlike the idea that there's some larger-than-earth body wandering around our solar system that neither we nor ancient astronomers have twigged to.

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    8. Re:Nothing Has Been Disproven Actually by Immerman · · Score: 1

      >Yes, but that was an idiotic idea because we could actually find it if it were that large

      Hardly - the thing could easily be on a highly elliptical long-period orbit, in which case we might only see it near it's closest approach, which could currently be hundreds or thousands of years away. Or we might not be able to see it at all, if it's surface was unusually dark.

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    9. Re:Nothing Has Been Disproven Actually by drinkypoo · · Score: 1

      >Yes, but that was an idiotic idea because we could actually find it if it were that large

      Hardly - the thing could easily be on a highly elliptical long-period orbit, in which case we might only see it near it's closest approach,

      Except it has to be closer than that to do the things it's claimed that it's doing...

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      "You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
    10. Re:Nothing Has Been Disproven Actually by Immerman · · Score: 3, Informative

      Not so. The proposed planet nine to explain the unlikely clustering of TNOs would have a period in the 10,000-20,000 year range https://en.wikipedia.org/wiki/...

      By Kepler's Law (T^2 proportional to R^3), that would put it's semi-major axis at between 464 to 737 AU, and its apogee could be almost twice that.(semimajor axis is the average of apogee and perigee)

      Assuming it basically looks like Pluto scaled up 11-23x (to the estimated 2-4x the Earth's diameter) Would mean it's angular diameter would be between (11x)*40AU/737AU = 0.6x and (23x)*40/464 = 2.0x the size, for an angular area between 0.36x and 4.0x Pluto, and a corresponding effective brightness between 0.6*(40/737)^2= 0.2% and 4.0*(40/464)^2=3% as bright as Pluto. Assuming a circular orbit - it might be far smaller and dimmer at apogee.

      Easy to overlook. Especially since it would move only 0.02 to 0.04 degrees per year. Or potentially much less it it's near apogee.

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  9. Re: Heil Hitlary by cyber-vandal · · Score: 1

    Why do I never see any of you geniuses explaining this to neo-Nazis? I'm sure they'd be most grateful for the heads-up.

  10. Seems counterintuitive... by Timothy2.0 · · Score: 1

    Wouldn't this just increase the chances of a Kuiper Belt planetoid if the total mass of Kuiper Belt objects was 10x that of Earth?

    1. Re:Seems counterintuitive... by PPH · · Score: 1

      a huge group of lesser masses that sum up to at least 10x Earth's mass

      I'd be interested in seeing what sort of distribution of smaller masses they assume. Particularly if one assumption is that they can all remain in stable orbits with respect to each other.

      --
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    2. Re:Seems counterintuitive... by Immerman · · Score: 1

      I would assume that they assume a elliptical torus of uniform density, (or possibly with some variation between perigee and apogee). That seems to be the usual approximation of rings.

      Stable orbits with respect to each other is rather the norm, is it not? After all, at a given distance from the primary, everything must be orbiting at the same speed.

      Rings are one of the most common mass distributions we see, and (so long as they're well outside the Roche limit) we don't completely understand why they do or don't consolidate into larger bodies. At any rate, if they *do* consolidate, it's presumed to take 10s to 100s of millions of years, and I can't find any information on whether that's influenced by the orbital period - if it is then at 30-50 AU, where orbits are in the 164-353 year range, it might take many billions of years for an Earth-sized planet to form, and it would still be in the early stages of the process.

      Plus, a radically lower mass density per cubic kilometer probably doesn't help anything - assuming a ring had 10x the total mass of Earth, it would have at best 1/3 to 1/5th the density of Earth's proto-planetary ring, and far, far lower if the radial width of the ring was several AU. That far from the primary the ring flattening effects would be much weaker/slower as well. All together, the density could easily be thousands or millions of times lower than Earth's protoplanetary disc, which would (presumably) make planet formation much less likely.

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    3. Re:Seems counterintuitive... by djinn6 · · Score: 1

      It should be a lot easier to verify a uniform ring of smaller objects. You can point the telescope at any point along the expected orbit and see a steady stream of objects.

      If we don't see that, then it would either be a tight clump in the process of turning into a planet, or a planet, or something completely different. After all, there could be other explanations for the orbits of eTNOs.

    4. Re:Seems counterintuitive... by Immerman · · Score: 1

      That would work great, if we had any way to see such objects. Before we went to visit up close and personal, this is one of the best photos we had of Pluto, a planet ~2400 km across. https://www.jpl.nasa.gov/space...

      A still-huge rock 1 km across would be about 6 million times smaller and dimmer (assuming the same surface albedo). It'd barely show up as a single very slightly less black pixel. More typical sized rocks in the 10-100m diameter? That's another 100x to 10,000x smaller and dimmer still. We wouldn't have a clue they were there.

      Also, there's no "steady stream of objects" implied, not from a human perspective anyway - at Pluto's orbital distance things are moving less than 1.5 degrees per year. And with a mass 10x Earth, spread out around an orbit that could hold a "necklace" of 3 million Earths, there's not necessarily going to be much in any give spot. Especially when you consider that the thickness of the Kuiper belt (perpendicular to the planetary plane) is larger than the diameter of Earth's orbit.

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    5. Re:Seems counterintuitive... by djinn6 · · Score: 1

      That photo of Pluto had a lot of pixels, but we really only need 1 to determine if there's anything there.

      Besides, we saw Ultima Thule didn't we? It would have to be a lot dimmer than even that before it's indistinguishable from noise.

  11. Re: Of course it can! by Type44Q · · Score: 1

    We would explain but you wouldn't grasp the answer. Don't feel bad; it's merely a cognitive thing. Lack thereof, rather..

  12. This study seems to almost step on its own tail. by dasunt · · Score: 2

    Currently, based on the sizes of the minor planets we have found beyond Neptune, as well as our chance of finding objects, one can extrapolate to a good possibility that we are missing something that is planet sized.

    If the mass of the Kuiper belt is far higher than expected, that makes it seem more likely that there is an undiscovered planet out there.

    I know this study is specifically about the hypothetical "Planet Nine", used to explain the clustering of some Sednoids. And its alternative explanation for that clustering may be correct. But overall, it seems to suggest that there's a unknown mechanism for adding more mass to the far outer reaches of the solar system.

  13. In a spherical shell net gravity is zero... by skaralic · · Score: 1

    Wouldn't a large number of small object in the Kuiper Belt essentially form a spherical shell with roughly uniformly distributed mass?

    http://hyperphysics.phy-astr.g...

    Given that, the net gravity and gravitational influence within would be zero so it wouldn't explain anything inside it...

    I guess the question is, are the strange orbits inside or outside of the "shell".