Researchers Find Evidence Of Distant Outer Planet |
Researchers Find Evidence Of Distant Outer Planet |
Jan 20 2016, 04:58 PM
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#1
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Member Group: Members Posts: 723 Joined: 13-June 04 Member No.: 82 |
Free to view paper:
Evidence for a Distant Giant Planet in the Solar System Konstantin Batygin and Michael E. Brown QUOTE Abstract Recent analyses have shown that distant orbits within the scattered disk population of the Kuiper Belt exhibit an unexpected clustering in their respective arguments of perihelion. While several hypotheses have been put forward to explain this alignment, to date, a theoretical model that can successfully account for the observations remains elusive. In this work we show that the orbits of distant Kuiper Belt objects (KBOs) cluster not only in argument of perihelion, but also in physical space. We demonstrate that the perihelion positions and orbital planes of the objects are tightly confined and that such a clustering has only a probability of 0.007% to be due to chance, thus requiring a dynamical origin. We find that the observed orbital alignment can be maintained by a distant eccentric planet with mass gsim10 m⊕ whose orbit lies in approximately the same plane as those of the distant KBOs, but whose perihelion is 180° away from the perihelia of the minor bodies. In addition to accounting for the observed orbital alignment, the existence of such a planet naturally explains the presence of high-perihelion Sedna-like objects, as well as the known collection of high semimajor axis objects with inclinations between 60° and 150° whose origin was previously unclear. Continued analysis of both distant and highly inclined outer solar system objects provides the opportunity for testing our hypothesis as well as further constraining the orbital elements and mass of the distant planet. QUOTE 6. SUMMARY To date, the distinctive orbital alignment observed within the scattered disk population of the Kuiper Belt remains largely unexplained. Accordingly, the primary purpose of this study has been to identify a physical mechanism that can generate and maintain the peculiar clustering of orbital elements in the remote outskirts of the solar system. Here, we have proposed that the process of resonant coupling with a distant, planetary mass companion can explain the available data, and have outlined an observational test that can validate or refute our hypothesis. We began our analysis with a re-examination of the available data. To this end, in addition to the previously known grouping of the arguments of perihelia (Trujillo & Sheppard 2014), we have identified ancillary clustering in the longitude of the ascending node of distant KBOs and showed that objects that are not actively scattering off of Neptune exhibit true orbital confinement in inertial space. The aim of subsequent calculations was then to establish whether gravitational perturbations arising from a yet-unidentified planetary-mass body that occupies an extended, but nevertheless bound, orbit can adequately explain the observational data. The likely range of orbital properties of the distant perturber was motivated by analytic considerations, originating within the framework of octupole-order secular theory. By constructing secular phase-space portraits of a strictly planar system, we demonstrated that a highly eccentric distant perturber can drive significant modulation of particle eccentricities and libration of apsidal lines such that the perturber's orbit continuously encloses interior KBOs. Intriguingly, numerical reconstruction of the projected phase-space portraits revealed that, in addition to secular interactions, resonant coupling may strongly affect the dynamical evolution of KBOs residing within the relevant range of orbital parameters. More specifically, direct N-body calculations have shown that grossly overlapped, apsidally anti-aligned orbits can be maintained at nearly Neptune-crossing eccentricities by a highly elliptical perturber, resulting in persistent near-colinearity of KBO perihelia. Having identified an illustrative set of orbital properties of the perturber in the planar case, we demonstrated that an inclined object with similar parameters can dynamically carve a population of particles that is confined both apsidally and nodally. Such sculpting leads to a family of orbits that is clustered in physical space, in agreement with the data. Although the model proposed herein is characterized by a multitude of quantities that are inherently degenerate with respect to one another, our calculations suggest that a perturber on an a' ~ 700 AU, e' ~ 0.6 orbit would have to be somewhat more massive (e.g., a factor of a few) than m' = 10 m⊕ to produce the desired effect. A unique prediction that arises within the context of our resonant coupling model is that the perturber allows for the existence of an additional population of high-perihelion KBOs that do not exhibit the same type of orbital clustering as the identified objects. Observational efforts aimed at discovering such objects, as well as directly detecting the distant perturber itself constitute the best path toward testing our hypothesis. So about the size of Neptune, if their hypothesis is correct. |
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Jan 28 2016, 09:56 AM
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#2
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Senior Member Group: Members Posts: 2346 Joined: 7-December 12 Member No.: 6780 |
Citing this article:
QUOTE The 0.007% chance that the clustering of the six objects is coincidental gives the planet claim a statistical significance of 3.8 sigma—beyond the 3-sigma threshold typically required to be taken seriously, but short of the 5 sigma that is sometimes used in fields like particle physics. The range between 3 and 5 sigma is usually called "evident", greater or equal 5 sigma is called "definitive". 3 < 3.8 < 5. That's all. The question is essentially, whether the numerical experimental settings leading to these 3.8 sigma confidence level are consistent with the way astronomers would have looked for the KBOs, hence whether the observational bias is considered appropriately. One issue might be, that the same arguments preventing the direct observation of a possible planet 9 prevented observations of KBOs, e.g. the densely crowded Milky Way background. Another issue might be an adjustment of the observation and detection methods to the first observed KBO of the presumed cluster. This disturbs the independence of the individual finds, as assumed in most randomized statistical tests, hence modifies inferred probabilities, and eventually the confidence level. Edit: Another example: The probability of six objects randomly found in the same predefined 0.203 fraction of the sky is 7e-5 (the 3.8 sigma); the probability of six objects randomly found in the same predefined 0.379 fraction of the sky is 3e-3 (3.0 sigma). Hence another uncertainty is the size of the region of the sky the six observations are assigned to. |
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Jan 28 2016, 11:09 AM
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#3
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
Part of the background of the complexity here is the high number of possible scenarios to model.
The possible scenarios involving a single large planet as the explanation allow for variation in several variables. The planet's mass is one variable and its orbit entails about three more. Ideally, modeling work could investigate a large number of the possible permutations, iterating over the range of possible values in a fine-grained way. To model the evolution of the outer solar system over eons in each of thousands of different scenarios is a feat requiring sheer CPU time, and that work certainly ought to be done. Then, we might learn if there are any combination of parameters that explain the observations, and which cannot do so. Examining only one, or even only 100, of the possibilities is just scratching the surface of the possibilities. Nobody, novice or professional, is going to work this out with mere deep thought. |
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Jan 28 2016, 03:09 PM
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#4
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Senior Member Group: Members Posts: 4256 Joined: 17-January 05 Member No.: 152 |
its orbit entails about three more The general orbit requires six parameters to describe it. If you assume it's orbital plane is close to the ecliptic that's still four parameters. Of course your point is well taken - it's going to be really hard to thoroughly explore that parameter space. |
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