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
Related Stories
Ethan Siegel at Starts With A Bang brings to attention the results of the Outer Solar System Origins Survey (OSSOS). The OSSOS project, which started in 2013 (before the Planet Nine hypothesis was proposed) to survey the minor planets of the outer Solar System, has discovered and determined the orbits of well over eight hundred trans-Neptunian objects (TNOs) in its operation. They have recently published a paper that basically puts the kibosh on the Planet Nine hypothesis. Planet Nine was initially proposed to explain an apparent anomalous clustering of orbits of TNOs consistent with them being perturbed by a large planet, but the OSSOS results have found no such anomalous clustering, and are rather seeing a distribution consistent with uniform randomness.
From Forbes' Javascript-required article:
It was perhaps the most exciting idea to come out of science last year: that an undiscovered, giant world exists in our Solar System, far beyond the orbit of Neptune. This wouldn't be some tiny, frozen world like Pluto or Eris, smaller even than Earth's Moon, but a monstrous super-Earth, perhaps ten times as massive as our own world and almost as large as Uranus or Neptune in radius. As the months passed since it was first proposed by Konstantin Batygin and Mike Brown, they compiled additional evidence for it, and things were looking rosy. But a new study by Shankman et al. has turned the evidence on its head, disfavoring the planet's existence and uncovering a bias in the data itself.
[...] what they found was entirely consistent with no Planet Nine, and that the overall case for Planet Nine's existence was substantially weakened by their study. In particular, the clustering in the orientation of each orbit in space (defined by multiple variables, ω and Ω) that earlier studies, like Batygin & Brown and Trujillo & Sheppard, previously noticed simply doesn't exist in this new, unbiased study.
We find no evidence in the OSSOS sample for the ω clustering that was the impetus for the current additional planet hypothesis.
The data from this new study is quite clear that the previously observed correlation, which was the impetus for hypothesizing Planet Nine, doesn't persist into the new sample.
OSSOS also has a Frequently Asked Questions page about these findings. They don't entirely rule out the existence of a substantial (perhaps Mars-sized) planet in the outer reaches of the Solar System, but their data makes it highly improbable that a super-Earth on the scale of Uranus or Neptune might be out there.
Additional reading:
https://www.sciencemag.org/news/2017/06/new-haul-distant-worlds-casts-doubt-planet-nine
Medieval astronomical records, such as the Bayeux Tapestry, could help narrow down the location (or at least infer the existence) of the hypothetical Planet Nine:
Scientists suspect the existence of Planet Nine because it would explain some of the gravitational forces at play in the Kuiper Belt, a stretch of icy bodies beyond Neptune. But no one has been able to detect the planet yet, though astronomers are scanning the skies for it with tools such as the Subaru Telescope on Hawaii's Mauna Kea volcano.
Medieval records could provide another tool, said Pedro Lacerda, a Queen's University astronomer and the other leader of the project.
"We can take the orbits of comets currently known and use a computer to calculate the times when those comets would be visible in the skies during the Middle Ages," Lacerda told Live Science. "The precise times depend on whether our computer simulations include Planet Nine. So, in simple terms, we can use the medieval comet sightings to check which computer simulations work best: the ones that include Planet Nine or the ones that do not."
Also at Queen's University Belfast.
Related: "Planet Nine" Might Explain the Solar System's Tilt
Planet Nine's Existence Disfavoured by New Data
Study of ETNOs Supports Planet Nine's Existence
Passing Star Influenced Comet Orbits in Our Solar System 70,000 Years Ago
2015 BP519, nicknamed "Caju", is another extreme trans-Neptunian object that points to the existence of Planet Nine. Discovered with data from the Dark Energy Survey, Caju has a relatively large diameter, estimated at around 400-700 km, meaning the object could be a gravitationally rounded dwarf planet. It also has a highly inclined orbit of 54°, which a team of scientists says can be explained by the presence of the hypothetical Planet Nine:
After discovering it, the team tried to investigate 2015 BP519's origins using computer simulations of the Solar System. However, these tests were not able to adequately explain how the object had ended with such an orbit.
But when the team added a ninth planet with properties exactly matching those predicted by the Caltech scientists in 2016, the orbit of 2015 BP519 suddenly made sense. "The second you put Planet Nine in the simulations, not only can you form objects like this object, but you absolutely do," Juliette Becker, a Michigan graduate student and lead author of the study told Quanta.
Some researchers, however, caution that Planet Nine may not be the only explanation for 2015 BP519's strange orbit. Michele Bannister, a planetary astronomer from Queen's University Belfast, in Ireland, who was not involved in the study, told Newsweek that while the latest findings were "a great discovery," other scenarios could account for its tilt. "This object is unusual because it's on a high inclination," she said. "This can be used to maybe tell us some things about its formation process. There are a number of models that suggest you can probably put objects like this into the shape of orbit and the tilt of orbit that we see today."
Also at Quanta Magazine.
Discovery and Dynamical Analysis of an Extreme Trans-Neptunian Object with a High Orbital Inclination (arXiv:1805.05355)
Related: Medieval Records Could Point the Way to Planet Nine
How we discovered 840 minor planets beyond Neptune – and what they can tell us
The new discoveries were made as part of a five year project called the Outer Solar System Origins Survey (OSSOS). The observations, conducted in 2013-2017, used the imaging camera of one of the world's major telescopes – the Canada-France-Hawaii Telescope on Maunakea in Hawaii. The survey looked for faint, slow-moving points of light within eight big patches of sky near the plane of the planets and away from the dense star fields of the Milky Way.
With 840 discoveries made at distances between six and 83 astronomical units (au) – one such unit is the distance between the sun and the Earth – the survey gives us a very good overview of the many sorts of orbits these "trans-Neptunian objects" have.
[...] We found 313 resonant trans-Neptunian objects, with the survey showing that they exist as far out as an incredible 130au – and are far more abundant than previously thought. Among these discoveries is the dwarf planet 2015 RR245, which is about half the size of Britain. It may have hopped onto its current orbit at 82au after an encounter with Neptune hundreds of millions of years ago. It was once among the 90,000 scattered objects of smaller size that we estimate currently exist.
The survey searched 155.3 square degrees of sky.
OSSOS. VII. 800+ Trans-Neptunian Objects—The Complete Data Release (open, DOI: 10.3847/1538-4365/aab77a) (DX)
The OSSOS discoveries include nine TNOs with q [perihelion] > 30 au and a [semimajor axis] > 150 au, eight of which have q > 38 au. [...] There has been recent interest in the apparent angular clustering of the MPC-listed TNOs with a > 150 au orbits, which some have hypothesized as evidence for a massive distant planet (Trujillo & Sheppard 2014; Batygin & Brown 2016). [...] Formation mechanisms for this distant population are not yet clear, and it remains an area of active investigation (e.g., Lawler et al. 2016; Nesvorny et al. 2017). However, all of the extreme TNO discoveries of OSSOS are consistent with a formation by random diffusion in semimajor axis due to weak kicks at perihelion by Neptune from orbits with semimajor axes in the inner fringe of the Oort cloud, as proposed in Bannister et al. (2017).
The Large Synoptic Survey Telescope (LSST) may be able to find new planets in our solar system, including the hypothesized planets Nine and Ten:
Overall, these estimates indicated that Planet 9/X was a super-Earth with anywhere between 5 to 20 Earth masses, and orbited the Sun at a distance of between 150 – 600 AU. Concurrently, these studies have also attempted to narrow down where this Super-Earth's orbit will take it throughout the outer Solar System, as evidenced by the perturbations it has on KBOs.
Unfortunately, the predicted locations and brightness of the object are not yet sufficiently constrained for astronomers to simply look in the right place at the right time and pick it out. In this respect, a large area sky survey must be carried out using moderately large telescopes with a very wide field of view. As Dr. Trilling told Universe Today via email:
"The predicted Planet X candidates are not particularly faint, but the possible locations on the sky are not very well constrained at all. Therefore, what you really need to find Planet X is a medium-depth telescope that covers a huge amount of sky. This is exactly LSST. LSST's sensitivity will be sufficient to find Planet X in almost all its (their) predicted configurations, and LSST will cover around half of the known sky to this depth. Furthermore, the cadence is well-matched to finding moving objects, and the data processing systems are very advanced. If you were going to design a tool to find Planet X, LSST is what you would design."
Astronomers have found a new crop of moons around Jupiter, and one of them is a weirdo
Ten more moons have been confirmed to orbit around Jupiter, bringing the planet's total known satellite count to 79. That's the highest number of moons of any planet in the Solar System. And these newly discovered space rocks are giving astronomers insight as to why the Jupiter system looks like it does today.
Astronomers at Carnegie Institution for Science first found these moons in March 2017, along with two others that were already confirmed in June of last year. The team initially found all 12 moons using the Blanco 4-meter telescope in Chile, though finding these objects wasn't their main goal. Instead, they were searching for incredibly distant small objects — or even planets — that might be lurking in our Solar System beyond Pluto. But as they searched for these fringe space rocks, they decided to take a peek at what might be lurking around Jupiter at the same time. Now, the moons they found have been observed multiple times, and their exact orbits have been submitted for approval from the International Astronomical Union, which officially recognizes celestial bodies.
These moons are all pretty tiny, ranging between less than a mile and nearly two miles wide. And they break down into three different types. Two orbit closer to Jupiter, moving in the same direction that the planet spins. Farther out from those, about 15.5 million miles from the planet, there are nine that rotate in the opposite direction, moving against Jupiter's rotation. But in this same distant region, one strange moon that astronomers are calling Valetudo is moving with Jupiter's spin, like the two inner moons.
Previously: Two Tiny New Moons Found Around Jupiter
Related: Retrograde Jupiter Co-Orbital Asteroid May Have an Interstellar Origin
Another Trans-Neptunian Object With a High Orbital Inclination Points to Planet Nine
CU Boulder Researchers Say Collective Gravity, Not Planet Nine, Explains Orbits of Detached Objects
Planet Nine: 'Insensitive' Term Riles Scientists
The International Astronomical Union (IAU) famously reclassified Pluto as a "dwarf planet" in 2006. That decision remains highly controversial today, as made clear by the new note, which appeared in the July 29 issue of the Planetary Exploration Newsletter.
The note:
ON THE INSENSITIVE USE OF THE TERM "PLANET 9" FOR OBJECTS BEYOND PLUTO
We the undersigned wish to remind our colleagues that the IAU planet definition adopted in 2006 has been controversial and is far from universally accepted. Given this, and given the incredible accomplishment of the discovery of Pluto, the harbinger of the solar system's third zone — the Kuiper Belt — by planetary astronomer Clyde W. Tombaugh in 1930, we the undersigned believe the use of the term 'Planet 9' for objects beyond Pluto is insensitive to Professor Tombaugh's legacy.
We further believe the use of this term should be discontinued in favor of culturally and taxonomically neutral terms for such planets, such as Planet X, Planet Next, or Giant Planet Five.
35 researchers signed the note, including Alan Stern, principal investigator of the New Horizons mission.
Of more interest may be this proposal concerning future exploration of Uranus and Neptune:
Related: Uranus and Neptune Are Potential Targets for 2030s Missions
Another Trans-Neptunian Object With a High Orbital Inclination Points to Planet Nine
CU Boulder Researchers Say Collective Gravity, Not Planet Nine, Explains Orbits of Detached Objects
Planet Nine Search Turns Up 10 More Moons of Jupiter
The search for Planet X gets a boost with the discovery of a super distant object
A new discovery is strengthening the idea that a large, mysterious planet — known as Planet 9 or Planet X — may be lurking unseen at the Solar System's edge. Astronomers say they have found a tiny object orbiting far out from the Sun that fits with the Planet X theory. In fact, the object may have even been pushed onto the path it takes now by this hidden planet's gravity.
The tiny rock — eloquently named TG387 and nicknamed "The Goblin" — was spotted by astronomers at the Carnegie Institution of Science using a giant Japanese observatory in Hawaii called Subaru. The Carnegie team first spotted the object in 2015 and then followed it on its journey around the Sun for the last four years. Those observations revealed an incredibly distant target. TG387 takes a whopping 40,000 years to complete just one orbit around the Sun. And it's on a very elliptical path far from the inner Solar System; the closest it ever gets to the Sun is 65 Astronomical Units (AU), or 65 times the distance between the Sun and the Earth. For reference, Pluto only gets as far as 49 AUs from the Sun.
This orbit is particularly enticing since it puts TG387 in a select group of distant Solar System objects that all point to the possible existence of Planet X. Right now, there are 14 far-out space rocks that all share similar orbit patterns, suggesting that this planet is out there. Their paths are all super elongated, and they all cluster together in the same area when they approach the Sun. Plus, their orbits are all tilted alike, and they point in the same general direction, as if something big has pushed them into similar places. These objects are the strongest lines of evidence astronomers have for Planet X, and finding a new one that matches this pattern reinforces that idea that this planet is more than just a theory.
Planet Nine and 2015 TG387.
Also at ScienceAlert, The Atlantic, USA Today, and NPR.
A New High Perihelion Inner Oort Cloud Object
Previously: Another Trans-Neptunian Object With a High Orbital Inclination Points to Planet Nine
CU Boulder Researchers Say Collective Gravity, Not Planet Nine, Explains Orbits of Detached Objects
Planet Nine Search Turns Up 10 More Moons of Jupiter
The strange orbits of some objects in the farthest reaches of our solar system, hypothesised by some astronomers to be shaped by an unknown ninth planet, can instead be explained by the combined gravitational force of small objects orbiting the Sun beyond Neptune, say researchers.
The alternative explanation to the so-called 'Planet Nine' hypothesis, put forward by researchers at the University of Cambridge and the American University of Beirut, proposes a disc made up of small icy bodies with a combined mass as much as ten times that of Earth. When combined with a simplified model of the solar system, the gravitational forces of the hypothesised disc can account for the unusual orbital architecture exhibited by some objects at the outer reaches of the solar system.
[...] "The Planet Nine hypothesis is a fascinating one, but if the hypothesised ninth planet exists, it has so far avoided detection," said co-author Antranik Sefilian, a PhD student in Cambridge's Department of Applied Mathematics and Theoretical Physics. "We wanted to see whether there could be another, less dramatic and perhaps more natural, cause for the unusual orbits we see in some TNOs. We thought, rather than allowing for a ninth planet, and then worry about its formation and unusual orbit, why not simply account for the gravity of small objects constituting a disc beyond the orbit of Neptune and see what it does for us?"
[...] Earlier attempts to estimate the total mass of objects beyond Neptune have only added up to around one-tenth the mass of Earth. However, in order for the TNOs to have the observed orbits and for there to be no Planet Nine, the model put forward by Sefilian and Touma requires the combined mass of the Kuiper Belt to be between a few to ten times the mass of Earth. [...] "It's also possible that both things could be true -- there could be a massive disc and a ninth planet. With the discovery of each new TNO, we gather more evidence that might help explain their behaviour."
Shepherding in a Self-Gravitating Disk of Trans-Neptunian Objects
Related: CU Boulder Researchers Say Collective Gravity, Not Planet Nine, Explains Orbits of Detached Objects
Corresponding with the three-year anniversary of their announcement hypothesizing the existence of a ninth planet in the solar system, Caltech's Mike Brown and Konstantin Batygin are publishing a pair of papers analyzing the evidence for Planet Nine's existence.
The papers offer new details about the suspected nature and location of the planet, which has been the subject of an intense international search ever since Batygin and Brown's 2016 announcement.
The first, titled "Orbital Clustering in the Distant Solar System," was published in The Astronomical Journal on January 22. The Planet Nine hypothesis is founded on evidence suggesting that the clustering of objects in the Kuiper Belt, a field of icy bodies that lies beyond Neptune, is influenced by the gravitational tugs of an unseen planet. It has been an open question as to whether that clustering is indeed occurring, or whether it is an artifact resulting from bias in how and where Kuiper Belt objects are observed.
To assess whether observational bias is behind the apparent clustering, Brown and Batygin developed a method to quantify the amount of bias in each individual observation, then calculated the probability that the clustering is spurious. That probability, they found, is around one in 500.
[...] The second paper is titled "The Planet Nine Hypothesis," and is an invited review that will be published in the next issue of Physics Reports. The paper provides thousands of new computer models of the dynamical evolution of the distant solar system and offers updated insight into the nature of Planet Nine, including an estimate that it is smaller and closer to the sun than previously suspected. Based on the new models, Batygin and Brown -- together with Fred Adams and Juliette Becker (BS '14) of the University of Michigan -- concluded that Planet Nine has a mass of about five times that of the earth and has an orbital semimajor axis in the neighborhood of 400 astronomical units (AU), making it smaller and closer to the sun than previously suspected -- and potentially brighter. Each astronomical unit is equivalent to the distance between the center of Earth and the center of the sun, or about 149.6 million kilometers.
-- submitted from IRC
The planet nine hypothesis (DOI: 10.1016/j.physrep.2019.01.009) (DX)
Orbital Clustering in the Distant Solar System (DOI: 10.3847/1538-3881/aaf051) (DX)
Previously: CU Boulder Researchers Say Collective Gravity, Not Planet Nine, Explains Orbits of Detached Objects
Where *Isn't* Planet 9? Search for Planet Nine still continues
Not long ago astronomers Mike Brown and Konstantin Batygin (the two original people proposing the existence of the planet) used the alignments of the TNO orbits to back-calculate the potential location of the unseen planet in space. It's a kind of treasure map to find the planet.
In a new paper they've put that map to use, looking through survey data in a hunt for Planet 9.
[...] Brown and Batygin wrote software that simulates where Planet 9 would be and how bright it would appears for various values of its size, reflectivity, and orbital shape. They created a database of positions and brightnesses for it, and then combed through the [Zwicky Transient Facility (ZTF)] database to look for it, going through the past three or so years of observations since the facility started its survey campaign.
[...] They ran 100,000 simulations of various parameters for the planet, and looked to see if the ZTF would've seen it if it were indeed smaller and closer to us. They determined that it would've been seen in the survey about 56,000 times out of the 100,000, so just looking at that their non-detection indicates the chance it's smaller and closer is now less than 50%, making it more likely it's farther out, bigger, and fainter.
The larger Vera C. Rubin Observatory is expected to find many previously hidden objects in the solar system, and is scheduled to begin full operations in October 2023. It will accumulate all-sky survey data around 10 times faster than the Zwicky Transient Facility.
Also at ExtremeTech.
(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/watch?v=aoFiw2jMy-0 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/watch?v=aoFiw2jMy-0 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/watch?v=aoFiw2jMy-0 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?