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Collective gravity, not Planet Nine, may explain the orbits of 'detached objects'
Bumper car-like interactions at the edges of our solar system—and not a mysterious ninth planet—may explain the the dynamics of strange bodies called "detached objects," according to a new study. CU Boulder Assistant Professor Ann-Marie Madigan and a team of researchers have offered up a new theory for the existence of planetary oddities like Sedna—an icy minor planet that circles the sun at a distance of nearly 8 billion miles. Scientists have struggled to explain why Sedna and a handful of other bodies at that distance look separated from the rest of the solar system. [...] The researchers presented their findings today at a press briefing at the 232nd meeting of the American Astronomical Society, which runs from June 3-7 in Denver, Colorado.
[...] [Jacob] Fleisig had calculated that the orbits of icy objects beyond Neptune circle the sun like the hands of a clock. Some of those orbits, such as those belonging to asteroids, move like the minute hand, or relatively fast and in tandem. Others, the orbits of bigger objects like Sedna, move more slowly. They're the hour hand. Eventually, those hands meet. "You see a pileup of the orbits of smaller objects to one side of the sun," said Fleisig, who is the lead author of the new research. "These orbits crash into the bigger body, and what happens is those interactions will change its orbit from an oval shape to a more circular shape." In other words, Sedna's orbit goes from normal to detached, entirely because of those small-scale interactions.
Also at Popular Mechanics, where Planet Nine proposer Konstantin Batygin disputes the findings:
Batygin, of Caltech, tells Popular Mechanics that any sufficiently strong gravitational encounter could detach an object from Neptune's embrace, but for the distant small bodies of the Kuiper belt to have done so through "self-gravity"—as the CU model proposes—there would need to be about five to ten times the mass of Earth in the outer parts of the Kuiper belt. There isn't.
"Unfortunately, the self-gravity story suffers from the following complications," Batygin says. "Both observational and theoretical estimates place the total mass of the Kuiper belt at a value significantly smaller than that of the Earth [only 1 to 10 percent Earth's mass]. As a consequence, Kuiper belt objects generally behave like test-particles enslaved by Neptune's gravitational pull, rather than a self-interacting group of planetoids."
Related: Planet Nine's Existence Disfavoured by New Data
Medieval Records Could Point the Way to Planet Nine
Another Trans-Neptunian Object With a High Orbital Inclination Points to Planet Nine
Outer Solar System Origins Survey Discovers Over 800 Trans-Neptunian Objects
LSST Could be the Key to Finding New Planets in Our Solar System
(Score: 5, Funny) by coolgopher on Tuesday June 05 2018, @02:08PM (2 children)
Oooh, science in action! Who will find the evidence which supports one hypothesis and contradicts the other? Who will throw in even more hypotheses into the mix? And who will come out of this not with the satisfaction of probably being right, but with the satisfaction of having pushed human knowledge further? Stay tuned, for more SCIENCE! :)
(Score: 2) by HiThere on Tuesday June 05 2018, @06:02PM (1 child)
The problem here is that while one could plausibly find an image of Planet 9, it's quite difficult to show that "a collection of comets playing bumper cars out in the Oort cloud" exists.
There math may be quite plausible (I don't know, and couldn't tell if they showed it to me), but that doesn't say that it's the correct answer, merely that it's one plausible scenario. And doesn't tell you how to check it.
IOW, this theory is only falsifiable by finding proof for a different explanation for the data. You can't directly prove it wrong (unless the math is wrong, and even then...).
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 3, Interesting) by khallow on Tuesday June 05 2018, @11:20PM
One can still carefully measure the orbits of the many objects in question to see if there's any collective deviation that can't be explained by the known Solar System and interaction between Kuiper Belt objects. A large mass can't hide forever.
(Score: 0) by Anonymous Coward on Tuesday June 05 2018, @04:36PM (4 children)
The Neptunians are just trying to keep everybody from finding their real home planet! They kept telling us it was in the Andromeda galaxy, but this transparent attempt to "control the narrative" outs their dastardly lies!!
(Score: 0) by Anonymous Coward on Tuesday June 05 2018, @04:47PM (1 child)
https://www.youtube.com/channel/UCiccT1eikDUoNFL1as2e9oQ/videos [youtube.com]
(Score: 0) by Anonymous Coward on Tuesday June 05 2018, @09:04PM
Nibiru is just another CIA cover story to make the Neptunians look like a craaazy conspiracy theory! Get with the times brah! Don't bury your head in the sand of gov sponsored lies, free yourself. Check out these videos for inspiration on how to change your life and be 100% self sufficient TRUTH OR SLAVERY [tinyurl.com]
(Score: 2) by All Your Lawn Are Belong To Us on Tuesday June 05 2018, @09:15PM (1 child)
Careful or you'll be taken to Neptanamo Bay. [wikia.com]
Fake Excuse.
This sig for rent.
(Score: 0) by Anonymous Coward on Tuesday June 05 2018, @10:42PM
Ha! Jokes on you I don't HAVE a lawn!!
(Score: 2) by c0lo on Tuesday June 05 2018, @11:30PM (4 children)
Did they repeal the third of the Kepler's law or amended the gravitational attraction?
Because I seem to remember that the orbit/period of satellites do not depend by the mass of the satellite.
So, at a given orbit radius, all bodies orbiting the star will have the same period no matter their mass.
(yes, I know this changes if one considers elliptical orbits, but then I never saw hands of a clock describing elliptic trajectories)
https://www.youtube.com/@ProfSteveKeen https://soylentnews.org/~MichaelDavidCrawford
(Score: 1, Informative) by Anonymous Coward on Wednesday June 06 2018, @01:48AM (3 children)
Newton's law of universal gravitation has the formula F = Gm1m2/r2. The force of gravity has dependence on BOTH the masses involved. For objects relatively near the sun though, the sun's mass is so much greater than that of any of the planets (it's several hundred times the mass of everything else in the solar system combined) that it becomes a reasonably good approximation to say that all bodies orbiting the star at the same distance have the same period. Everything changes though if you had a body whose mass is in the range of the sun's: if we had a white dwarf, neutron star, or other similarly massive object its orbit would be rather different than if you had a much lighter object like an ordinary planet: the sun and the notional object would instead be orbiting around their common centre of mass. If we had, say, the sun with a white dwarf of exactly one solar mass at 1 AU, the orbital period would not be exactly one year, but more like 258 days (sqrt(2)/2 × 1 year). The difference gets smaller the greater the mass difference gets, so even for Jupiter, which is less than a thousandth of the sun's mass, Kepler's approximation is still reasonable.
In the distant reaches of the solar system though, the sun's gravitational influence is weaker (see that r2 in the denominator of the formula above?), and the gravitational influence of far less massive, but much closer objects becomes a significant factor in their dynamics, which can become rather chaotic (see the three-body problem).
(Score: 2) by c0lo on Wednesday June 06 2018, @04:12AM (2 children)
The thing that I grumbled against is the impression the way they presented their explanation: smaller asteroids are faster (because they are smaller?) and the massive Sedna move slower (because it is bigger?)
When discussing the trajectories of bodies with masses much smaller than the Sun, the mass of the object becomes irrelevant for the trajectory they go under the Sun's gravitational pull - a feather and a cannonball (considered as material points) will orbit the same way around the Sun given the same initial velocity and position.
But we aren't in such a case for the context of TFA.
Yes, the many-body problem is relevant to what happens to the orbits of Kuiper-belt bodies. But the object there are "about the same distance from the Sun", so what would be the reasons to have the smaller asteroids "periodically congregating in big crowds to annoy Sedna, only to disperse after they upset it enough"?
(Remember those news about the catastrophes "about to happen in May 2000" [tkcs-collins.com], with 6 planets aligning?)
https://www.youtube.com/@ProfSteveKeen https://soylentnews.org/~MichaelDavidCrawford
(Score: 0) by Anonymous Coward on Wednesday June 06 2018, @05:40AM (1 child)
Sedna is at 1.4×1010 km from the sun. The gravitational acceleration from the sun for an object at that distance is something like 6.8×10-7 m/s2. The mass of Sedna is still unknown at this time, but it is not unreasonable to estimate it at 1021 kg (less than Pluto or Eris). An object about, say, 500,000 km from it (of the order of the distance from the earth to the moon), also experiences an acceleration due to Sedna's gravity comparable to what it is getting from the sun, roughly 3×10-7 m/s2. Think of what that means for a second: a body like Sedna has about as much influence over the trajectories of objects somewhat close to it as the sun does. It's easy to see how smaller KBOs close to Sedna might have dynamics that look like them periodically congregating in crowds to "annoy Sedna" and then later disperse as their altered trajectories fling them away. With a relatively large object out there with a gravitational influence comparable to the sun's at that distance they'd definitely not just be drifting about in neat, orderly Keplerian orbits!
An even bigger body like the hypothetical Planet 9 would be a really noticeable influence on objects close to it out there. If, as hypothesised, it had ten earth masses, it would be able to exert accelerations of 0.02 m/s2 on bodies half a million kilometres from it (roughly as much as that experienced by a body at 0.5 AU from the sun, just a little further than Mercury's orbit). In contrast, at 700 AU (planet nine's hypothesised distance), the sun's influence on those objects close to it would be a measly 1.2×10-8 m/s2.
(Score: 2) by c0lo on Wednesday June 06 2018, @07:47AM
I can accept that the dynamics may allow smaller KBO to show a "congregation"-like behaviour (being fling after the encounter with altered objects, or having some of them even accreting them on Sedna). I doubt though that we can observe a periodicity - because those objects will likely be thrown from their orbit and there's no guarantee that others with similar distribution space/velocity distribution will be available for a "future annoying encounter"; it's more likely to assist to a dynamic (deterministic) chaos of such events; at least until Sedna clears its orbit (the smaller KBO objects need to be close to Sedna to speak about meaningful n-body conditions, thus it's likely those objects will be in the close neighbourhood)
https://www.youtube.com/@ProfSteveKeen https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by Azuma Hazuki on Wednesday June 06 2018, @03:51AM (1 child)
...is no one wants to read any more awful Sailor Moon fanfiction with OCs in it. Add a new planet, and guess what happens? Yup, another guardian.
I am "that girl" your mother warned you about...
(Score: 0) by Anonymous Coward on Wednesday June 06 2018, @08:30AM
But you can have guardians of asteroids and moons already, so… too late!
(Score: 0) by Anonymous Coward on Wednesday June 06 2018, @08:17AM
I don't understand the dispute. The dispute of the new theory argues that there is insufficient mass for the theory to be valid, therefore it must be the very massive new planet theory?