Is Planet Nine almost certain, probable, possible or unlikely?

[Hornblower]

In 1992, the discovery of a small object unlocked a big secret: that the solar system was far more vast than we’d ever imagined. Before, we’d only confirmed the existence of lonely, strange, cold Pluto, in a region of space called the Kuiper Belt. The Kuiper Belt is a grouping of icy objects located in an area just outside the orbit of Neptune—like a colder, more watery asteroid belt. Up until 1992, it had been strictly theoretical because no one had observed anything beyond Pluto. The discovery of 1992 QB1 marked only the second time an object in the Kuiper Belt had been found. In the next few years, discoveries of these small, cold worlds snowballed—80+ were found between 1992 and 1999, and hundreds are known today. With the outer solar system surveys at Mauna Kea and La Palma observatories in the 1990s, we finally began to unlock the “third zone” of the solar system as something more than theoretical.

First the author says the solar system was more vast than we had ever imagined, and then he acknowledges that there were theories about stuff beyond Pluto. That means we had imagined it. Yet another example of questionable writing by a popular media writer.

[kzb]

First the author says the solar system was more vast than we had ever imagined, and then he acknowledges that there were theories about stuff beyond Pluto. That means we had imagined it. Yet another example of questionable writing by a popular media writer.

Pedants' Corner

If you assume the word "we" refers to a section or grouping of people who had never imagined this, but there are other people who are not members of this group, strictly speaking it makes grammatical sense.

It's not what he or she meant though !

[George]

How much nicer it would have been for the author to have presented the history of the Belt’s existence by going from early speculations by several scientists to real hypotheses, which doesn’t compare as well as is suggested for this new region.

[selvaarchi]

Now another explanation for the erratic movement of these worlds in the Kuiper belt. This explanation does not need a planet 9.

https://www.colorado.edu/today/2018/...ective-gravity

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.

One theory suggests that an as-of-yet-unseen ninth planet lurking beyond Neptune may have kicked up the orbits of these detached objects.

But Madigan and her colleagues calculated that the orbits of Sedna and its ilk may result from these bodies jostling against each other and space debris in the outer solar system.

“There are so many of these bodies out there. What does their collective gravity do?” said Madigan of the Department of Astrophysical and Planetary Sciences (APS) and JILA. “We can solve a lot of these problems by just taking into account that question.”

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.

[Tom Mazanec]

On the other hand, here is a suggestion that Sedna et al may have been perturbed by numerous planetoids:
https://www.colorado.edu/today/2018/...ective-gravity

[peteshimmon]

One thing about that citizen science project looking for the planet, if anyone succeeds and flags up the thing will they be allowed to become immortal?

[kzb]

One thing about that citizen science project looking for the planet, if anyone succeeds and flags up the thing will they be allowed to become immortal?

Presuming you mean will they name the planet after its discoverer, that seems unlikely to me. The IAU has sole competency in recognising planet names. All other recognised planets have names from ancient mythology.

"Eris" was not called "Brown" for example, and that is only a dwarf planet. The naming of a proper large planet would come under even more scrutiny.

Having said that, the discoverer will be immortal as the discoverer.

[George]

Presuming you mean will they name the planet after its discoverer, that seems unlikely to me. The IAU has sole competency in recognising planet names. All other recognised planets have names from ancient mythology.

Yes, there was once a planet named George. Perhaps Herschel didn't help things with this, though I kinda like it for some reason.

[ronin]

Now another explanation for the erratic movement of these worlds in the Kuiper belt. This explanation does not need a planet 9.

https://www.colorado.edu/today/2018/...ective-gravity

Is it possible that the occasional close passage of other Stars could also have caused the observed erratic orbits?

[A.DIM]

From Space.com:

The collective-gravity hypothesis isn't a silver bullet, however. For example, there's still "clustering in pomega," which Madigan described as the odd fact that the orbits of the detached objects all tilt the same way.
"Planet Nine explains this really well, and we do not," Madigan said.
Ironically, while the new research discounts the need for an undiscovered planet, it requires the presence of thousands of smaller unseen objects.

"Take your pick," it would seem, but I know which way I tilt. Ha!

[ngc3314]

Yes, there was once a planet named George. Perhaps Herschel didn't help things with this, though I kinda like it for some reason.

I have read that, several decades later, Leverrier was interested in reviving that designation.

[George]

I have read that, several decades later, Leverrier was interested in reviving that designation.

A Frenchman honoring King George? . That’s surprising. He was credited for discovering, via the math of dancing George, Neptune, which was, apparently, his suggestion. That might have something to do with supporting Herschel but I doubt it. Any idea why he would favor George? Did he have inside info on a plot by the Germans to consciously engage in planetary naming pun-ishment? I doubt that, too.

Saturn...George...Jean...Clyde. I like it.

[Roger E. Moore]

I was looking through the abstracts when a single word leaped out at me. I realized then I had not kept up with the latest Outer Planet research at all.

============================

http://adsabs.harvard.edu/abs/2018AJ....155..243T

On the Detectability of Planet X with LSST

Trilling, David E.; Bellm, Eric C.; Malhotra, Renu
06/2018

TWO planetary mass objects in the far outer solar system---collectively referred to here as Planet X--- have recently been hypothesized to explain the orbital distribution of distant Kuiper Belt Objects. Neither planet is thought to be exceptionally faint, but the sky locations of these putative planets are poorly constrained. Therefore, a wide area survey is needed to detect these possible planets. The Large Synoptic Survey Telescope (LSST) will carry out an unbiased, large area (around 18000 deg2), deep (limiting magnitude of individual frames of 24.5) survey (the ``wide-fast-deep (WFD)'' survey) of the southern sky beginning in 2022, and it will therefore be an important tool in searching for these hypothesized planets. Here, we explore the effectiveness of LSST as a search platform for these possible planets. Assuming the current baseline cadence (which includes the WFD survey plus additional coverage), we estimate that LSST will confidently detect or rule out the existence of Planet X in 61% of the entire sky. At orbital distances up to ~75 au, Planet X could simply be found in the normal nightly moving object processing; at larger distances, it will require custom data processing. We also discuss the implications of a nondetection of Planet X in LSST data.

=============================

[Emphasis mine.] I went to the article itself, and lo, it was not TWO Planet X's, it seemed to be a LOT. Or maybe just disagreements about ONE. Hard to tell.

=============================

https://arxiv.org/pdf/1804.07713.pdf

"The possibility of undiscovered planets in the solar system has long fascinated astronomers and the public alike. Recent studies of the orbital properties of very distant Kuiper belt objects (KBOs) have identified several anomalies that may be due to the gravitational influence of one or more undiscovered planetary mass objects orbiting the Sun at distances comparable to the distant KBOs. Trujillo & Sheppard (2014) and Sheppard & Trujillo (2016) noted a clustering of the argument of perihelion (the angular position of the perihelion relative to the ascending node of an orbit on the J2000 reference plane) of KBOs whose semi-major axes exceed 150 au. Subsequently, Batygin & Brown (2016) and Brown & Batygin (2016) noted a clustering of the longitudes of perihelion and of the orbit poles of the same group of distant KBOs. Malhotra et al. (2016) noted that the most distant KBOs have near-integer period ratios, suggestive of dynamical resonances with a massive perturber. These orbital distribution peculiarities could be caused by an unseen massive body. Trujillo & Sheppard (2014) estimate a super-Earth mass object orbiting at a heliocentric distance & 250 au (while noting that a range of parameters for an unseen parameter could produce the observational signature that they observe); Brown & Batygin (2016) estimate a planet of mass 5–20 M⊕ in an orbit of semi-major axis 380–980 au, perihelion distance 150–350 au and moderately inclined (~30◦) to the ecliptic; and Malhotra et al. (2016) suggest a ~10 M⊕ planet in an orbit of semi-major axis ~665 au of moderate eccentricity and two possible inclinations (i  18◦ or i  48◦ to the ecliptic). The observational sample size for the above analyses is relatively small, 6–13 objects, depending upon choice of perihelion distance cut-off. Finally, in a separate line of argument, Bailey et al. (2016) and Gomes et al. (2017) show that the obliquity of the Sun of around 6 degrees can be explained by a 10–20 M⊕ perturber with a semi-major axis of 400–600 au. Separately, for a larger sample of ~160 distant KBOs whose semi-major axes are in the range 50–80 au, Volk & Malhotra (2017) reported a strong deviation of the mid-plane from the Solar System’s invariable plane. Based on this deviation, they suggest the presence of a smaller planetary mass object of mass 0.1–2.4 M⊕ at distance 60–100 au in an orbit inclined to the ecliptic by a few to a few tens of degrees. The predicted locations (in the sky) and brightnesses for these massive unseen objects — here referred to collectively as “Planet X” — are sufficiently unconstrained that large area sky surveys must be carried out. Such surveys require moderately large telescopes — a distant planet may be as bright as V=15 (Volk & Malhotra 2017) or as faint as V=22–25 (Brown & Batygin 2016) — and very large fields of view, as the search regions are at least hundreds of square degrees, and could easily be thousands.

[Roger E. Moore]

NEW PAPER!!

https://arxiv.org/abs/1808.01248

The Influence of Planet 9 on the Orbits of Distant TNOs: The Case for a Low Perihelion Planet

Jessica Cáceres, Rodney Gomes
(Submitted on 3 Aug 2018)

The hypothesis of an additional planet in the outer Solar System has gained new support as a result of the confinement noted in the angular orbital elements of distant trans-Neptunian objects. Orbital parameters proposed for the external perturber suggest semimajor axes between 500 and 1000 au, perihelion distances between 200 and 400 au for masses between 10 and 20 M⊕. In this paper we study the possibility that lower perihelion distances for the additional planet can lead to angular confinements as observed in the population of objects with semimajor axes greater than 250 au and perihelion distances higher than 40 au. We performed numerical integrations of a set of particles subjected to the influence of the known planets and the putative perturber during the age of the Solar System and compared our outputs with the observed population through a statistical analysis. Our investigations showed that lower perihelion distances from the outer planet usually lead to more substantial confinements than higher ones, while retaining the Classical Kuiper Belt as well as the ratio of the number of detached with perihelion distances higher than 42 au to scattering objects in the range of semimajor axes from 100 au to 200 au.

[Roger E. Moore]

https://arxiv.org/abs/1805.05355

Discovery and Dynamical Analysis of an Extreme Trans-Neptunian Object with a High Orbital Inclination

J. C. Becker, T. Khain, S. J. Hamilton, F. Adams, D. W. Gerdes, L. Zullo, K. Franson, S. Millholland, G. M. Bernstein, M. Sako, P. Bernardinelli, K. Napier, L. Markwardt, Hsing Wen Lin, W. Wester, F. B. Abdalla, S. Allam, J. Annis, S. Avila, E. Bertin, D. Brooks, A. Carnero Rosell, M. Carrasco Kind, J. Carretero, C. E. Cunha, C. B. D'Andrea, L. N. da Costa, C. Davis, J. De Vicente, H. T. Diehl, P. Doel, T. F. Eifler, B. Flaugher, P. Fosalba, J. Frieman, J. Garcia-Bellido, E. Gaztanaga, D. Gruen, R. A. Gruendl, J. Gschwend, G. Gutierrez, W. G. Hartley, D. L. Hollowood, K. Honscheid, D. J. James, K. Kuehn, N. Kuropatkin, M. A. G. Maia, M. March, J. L. Marshall, F. Menanteau, R. Miquel, R. L. C. Ogando, A. A. Plazas, E. Sanchez, V. Scarpine, R. Schindler, I. Sevilla-Noarbe, M. Smith, R. C. Smith, et al. (5 additional authors not shown)
(Submitted on 14 May 2018 (v1), last revised 6 Aug 2018 (this version, v2))

We report the discovery and dynamical analysis of 2015 BP519, an extreme Trans-Neptunian Object detected by the Dark Energy Survey at a heliocentric distance of 55 AU and absolute magnitude Hr= 4.3. The current orbit, determined from a 1110-day observational arc, has semi-major axis a≈450 AU, eccentricity e≈0.92 and inclination i≈54 degrees. With these orbital elements, 2015 BP519 is the most extreme TNO discovered to date, as quantified by the reduced Kozai action, which is a conserved quantity at fixed semi-major axis a for axisymmetric perturbations. We discuss the orbital stability and evolution of this object in the context of the known Solar System, and find that 2015 BP519 displays rich dynamical behavior, including rapid diffusion in semi-major axis and more constrained variations in eccentricity and inclination. We also consider the long term orbital stability and evolutionary behavior within the context of the Planet Nine Hypothesis, and find that BP519 adds to the circumstantial evidence for the existence of this proposed new member of the Solar System, as it would represent the first member of the population of high-i,
ϖ-shepherded TNOs.

[Roger E. Moore]

https://arxiv.org/abs/1712.06547

Chaotic Dynamics of Trans-Neptunian Objects Perturbed by Planet Nine

Sam Hadden, Gongjie Li, Matthew J. Payne, Matthew J. Holman
(Submitted on 18 Dec 2017 (v1), last revised 1 May 2018 (this version, v2))

Observations of clustering among the orbits of the most distant trans-Neptunian objects (TNOs) has inspired interest in the possibility of an undiscovered ninth planet lurking in the outskirts of the solar system. Numerical simulations by a number of authors have demonstrated that, with appropriate choices of planet mass and orbit, such a planet can maintain clustering in the orbital elements of the population of distant TNOs, similar to the observed sample. However, many aspects of the rich underlying dynamical processes induced by such a distant eccentric perturber have not been fully explored. We report the results of our investigation of the dynamics of coplanar test-particles that interact with a massive body on an circular orbit (Neptune) and a massive body on a more distant, highly eccentric orbit (the putative Planet Nine). We find that a detailed examination of our idealized simulations affords tremendous insight into the rich test-particle dynamics that are possible. In particular, we find that chaos and resonance overlap plays an important role in particles' dynamical evolution. We develop a simple mapping model that allows us to understand, in detail, the web of overlapped mean-motion resonances explored by chaotically evolving particles. We also demonstrate that gravitational interactions with Neptune can have profound effects on the orbital evolution of particles. Our results serve as a starting point for a better understanding of the dynamical behavior observed in more complicated simulations that can be used to constrain the mass and orbit of Planet 9.

[Roger E. Moore]

https://arxiv.org/abs/1712.04950

A 3pi Search for Planet Nine at 3.4 microns with WISE and NEOWISE

A. M. Meisner, B. C. Bromley, S. J. Kenyon, T. E. Anderson
(Submitted on 13 Dec 2017)

The recent 'Planet Nine' hypothesis has led to many observational and archival searches for this giant planet proposed to orbit the Sun at hundreds of astronomical units. While trans-Neptunian object searches are typically conducted in the optical, models suggest Planet Nine could be self-luminous and potentially bright enough at ~3-5 microns to be detected by the Wide-field Infrared Survey Explorer (WISE). We have previously demonstrated a Planet Nine search methodology based on time-resolved WISE coadds, allowing us to detect moving objects much fainter than would be possible using single-frame extractions. In the present work, we extend our 3.4 micron (W1) search to cover more than three quarters of the sky and incorporate four years of WISE observations spanning a seven year time period. This represents the deepest and widest-area WISE search for Planet Nine to date. We characterize the spatial variation of our survey's sensitivity and rule out the presence of Planet Nine in the parameter space searched at W1 < 16.7 in high Galactic latitude regions (90% completeness).

[Roger E. Moore]

https://arxiv.org/abs/1807.03371

Limits on the number of primordial Scattered Disk objects at Pluto mass and higher from the absence of their dynamical signatures on the present day trans-Neptunian Populations

Andrew Shannon, Rebekah I. Dawson
(Submitted on 9 Jul 2018 (v1), last revised 17 Jul 2018 (this version, v2))

Today, Pluto and Eris are the largest and most massive Trans-Neptunian Objects respectively. They are believed to be the last remnants of a population of planetesimals that has been reduced by >99% since the time of its formation. This reduction implies a primordial population of hundreds or thousands of Pluto-mass objects, and a mass-number distribution that could have extended to hundreds of Lunas, dozens of Mars, and several Earths. Such lost protoplanets would have left signatures in the dynamics of the present-day Trans-Neptunian Populations, and we statistically limit their primordial number by considering the survival of ultra-wide binary TNOs, the Cold Classical Kuiper belt, and the resonant population. We find that if the primordial mass-number distribution extended to masses greater than Pluto (~1e-3 Earth masses), it must have turned downwards to be no more top-heavy than roughly equal mass per log size, a significant deviation from the distribution observed between 1e-5 and 1e-3 Earth masses. We compare these limits to the predicted mass-number distribution of various planetesimal and proto-planet growth models. The limits derived here provide a test for future models of planetesimal formation.

=============

https://arxiv.org/abs/1803.06245

Resonances in the asteroid and trans-Neptunian belts: a brief review

Tabare Gallardo
(Submitted on 16 Mar 2018)

Mean motion resonances play a fundamental role in the dynamics of the small bodies of the Solar System. The last decades of the 20th century gave us a detailed description of the dynamics as well as the process of capture of small bodies in coplanar or small inclination resonant orbits. More recently, semianalytical or numerical methods allowed us to explore the behavior of resonant motions for arbitrary inclination orbits. The emerging dynamics is very rich, including large orbital changes due to secular effects inside mean motion resonances. The process of capture in highly inclined or retrograde resonant orbits was addressed showing that the capture in retrograde resonances is more efficient than in direct ones. A new terminology appeared in order to characterize the properties of the resonances. Numerical explorations in the transneptunian region showed the relevance and the particular dynamics of the exterior resonances with Neptune which can account for some of the known high perihelion orbits in the scattered disk. Moreover, several asteroids evolving in resonance with planets other than Jupiter or Neptune were found and a large number of asteroids in three-body resonances were identified.

[Roger E. Moore]

Apologies if any of these articles were previously mentioned; I checked but did not confirm duplication. Here are some "new" (unmentioned) 2018 articles on Planet X and the outer Solar System past Neptune.

https://arxiv.org/abs/1806.06867

The Secular Dynamics of TNOs and Planet Nine Interactions

Gongjie Li, Samuel Hadden, Matthew Payne, Matthew J. Holman
(Submitted on 18 Jun 2018)

The existence of Planet Nine has been suggested to explain the pericenter clustering of extreme trans-Neptunian objects (TNOs). However, the underlying dynamics involving Planet Nine, test particles and Neptune is rich, and it remains unclear which dynamical processes lead to the alignment and how they depends on the properties of Planet Nine. Here, we investigate the secular interactions between an eccentric outer perturber and TNOs starting in a near-coplanar configuration. We find that a large number of TNOs could survive outside of mean motion resonances at 4Gyr, which differs from previous results obtained in the exact coplanar case with Neptune being treated as a quadrupole potential. In addition, secular dynamics leads to the orbital clustering seen in N-body simulations. We find that a near coplanar Planet Nine can flip TNO orbital planes, and when this happens, the geometrical longitudes of pericenter of the TNOs librate around 180 ∘ during the flip. Orbital precession caused by the inner giant planets can suppress the flips while keeping the longitude of pericenter librating when 30 ≲ rp ≲ 80 AU & a ≳ 250 AU. This results in the alignment of the pericenter of the low inclination TNOs (i ≲ 40∘). We find the anti-aligned population and the flipped orbits could be produced by an eccentric (e 9 ≳ 0.4) outer planet of ∼10 M⊕ in a wide a9 ≳ 400∼800 AU orbit. Future surveys on the high inclination TNOs will help further constrain the properties of possible outer planets.

=============================

https://arxiv.org/abs/1805.01203

A new approach to distant solar system object detection in large survey data sets

V. Perdelwitz, M. Völschow, H. M. Müller
(Submitted on 3 May 2018)

The recently postulated existence of a giant ninth planet in our solar system has sparked search efforts for distant solar system objects (SSOs) both via new observations and archival data analysis. Due to the likely faintness of the object in the optical and infrared regime, it has so far eluded detection. We set out to re-analyze data acquired by the Wide-Field Infrared Survey Explorer (WISE), an all-sky survey well suited for the detection of SSOs. We present a new approach to SSO detection via parallactic fitting. Using the heliocentric distance as a fit parameter, our code transforms groups of three or more single observation point sources to heliocentric coordinates under the assumption that all data stem from an object. The fact that the orbit of a distant SSO is approximately linear in heliocentric coordinates over long time-scales can be utilized to produce candidates, which can then be confirmed with follow-up observations. We demonstrate the feasibility of the approach by a posteriori detecting the outer SSO Makemake within WISE data. An all-sky search for Planet Nine yielded no detection. While the postulated Planet Nine eluded detection by our algorithm, we tentatively predict that this new approach to moving-object analysis will enable the discovery of new distant SSOs that cannot be discovered by other algorithms. Especially in cases of sparse data observed over long time spans, our approach is unique and robust due to the use of only one fit parameter.

=======================

http://iopscience.iop.org/article/10...881/aaccf4/pdf

Feasibility of a Resonance-based Planet Nine Search

Bailey, Elizabeth; Brown, Michael E.; Batygin, Konstantin
08/2018

It has been proposed that mean-motion resonances (MMRs) between Planet Nine and distant objects of the scattered disk might inform the semimajor axis and instantaneous position of Planet Nine. Within the context of this hypothesis, the specific distribution of occupied MMRs largely determines the available constraints. Here we characterize the behavior of scattered Kuiper Belt objects arising in the presence of an eccentric Planet Nine (e 9 ∈ 0.1, 0.7), focusing on relative sizes of populations occupying particular commensurabilities. Highlighting the challenge of predicting the exact MMR of a given object, we find that the majority of resonant test particles have period ratios with Planet Nine other than those of the form P 9/P = N/1, N/2 (N ∈ Z+). Taking into account the updated prior distribution of MMRs outlined in this work, we find that the close spacing of high-order resonances, as well as chaotic transport, preclude resonance-based Planet Nine constraints from current observational data.

======================

https://arxiv.org/abs/1804.11281

The Generation of the Distant Kuiper Belt by Planet Nine from an Initially Broad Perihelion Distribution

Tali Khain, Konstantin Batygin, Michael E. Brown
(Submitted on 30 Apr 2018)

The observation that the orbits of long-period Kuiper Belt objects are anomalously clustered in physical space has recently prompted the Planet Nine hypothesis - the proposed existence of a distant and eccentric planetary member of our solar system. Within the framework of this model, a Neptune-like perturber sculpts the orbital distribution of distant Kuiper Belt objects through a complex interplay of resonant and secular effects, such that in addition to perihelion-circulating objects, the surviving orbits get organized into apsidally aligned and anti-aligned configurations with respect to Planet Nine's orbit. In this work, we investigate the role of Kuiper Belt initial conditions on the evolution of the outer solar system using numerical simulations. Intriguingly, we find that the final perihelion distance distribution depends strongly on the primordial state of the system, and demonstrate that a bimodal structure corresponding to the existence of both aligned and anti-aligned clusters is only reproduced if the initial perihelion distribution is assumed to extend well beyond ∼36 AU. The bimodality in the final perihelion distance distribution is due to the existence of permanently stable objects, with the lower perihelion peak corresponding to the anti-aligned orbits and the higher perihelion peak corresponding to the aligned orbits. We identify the mechanisms which enable the persistent stability of these objects and locate the regions of phase space in which they reside. The obtained results contextualize the Planet Nine hypothesis within the broader narrative of solar system formation, and offer further insight into the observational search for Planet Nine.

=========================

https://arxiv.org/abs/1712.06547

Chaotic Dynamics of Trans-Neptunian Objects Perturbed by Planet Nine

Sam Hadden, Gongjie Li, Matthew J. Payne, Matthew J. Holman
(Submitted on 18 Dec 2017 (v1), last revised 1 May 2018 (this version, v2))

Observations of clustering among the orbits of the most distant trans-Neptunian objects (TNOs) has inspired interest in the possibility of an undiscovered ninth planet lurking in the outskirts of the solar system. Numerical simulations by a number of authors have demonstrated that, with appropriate choices of planet mass and orbit, such a planet can maintain clustering in the orbital elements of the population of distant TNOs, similar to the observed sample. However, many aspects of the rich underlying dynamical processes induced by such a distant eccentric perturber have not been fully explored. We report the results of our investigation of the dynamics of coplanar test-particles that interact with a massive body on an circular orbit (Neptune) and a massive body on a more distant, highly eccentric orbit (the putative Planet Nine). We find that a detailed examination of our idealized simulations affords tremendous insight into the rich test-particle dynamics that are possible. In particular, we find that chaos and resonance overlap plays an important role in particles' dynamical evolution. We develop a simple mapping model that allows us to understand, in detail, the web of overlapped mean-motion resonances explored by chaotically evolving particles. We also demonstrate that gravitational interactions with Neptune can have profound effects on the orbital evolution of particles. Our results serve as a starting point for a better understanding of the dynamical behavior observed in more complicated simulations that can be used to constrain the mass and orbit of Planet 9.

====================

https://arxiv.org/abs/1710.08295

Circularizing Planet Nine through dynamical friction with an extended, cold planetesimal belt

Linn E.J. Eriksson, Alexander J. Mustill, Anders Johansen
(Submitted on 23 Oct 2017 (v1), last revised 10 Jan 2018 (this version, v2))

Unexpected clustering in the orbital elements of minor bodies beyond the Kuiper belt has led to speculations that our solar system actually hosts nine planets, the eight established plus a hypothetical "Planet Nine". Several recent studies have shown that a planet with a mass of about 10 Earth masses on a distant eccentric orbit with perihelion far beyond the Kuiper belt could create and maintain this clustering. The evolutionary path resulting in an orbit such as the one suggested for Planet Nine is nevertheless not easily explained. Here we investigate whether a planet scattered away from the giant-planet region could be lifted to an orbit similar to the one suggested for Planet Nine through dynamical friction with a cold, distant planetesimal belt. Recent simulations of planetesimal formation via the streaming instability suggest that planetesimals can readily form beyond 100au. We explore this circularisation by dynamical friction with a set of numerical simulations. We find that a planet that is scattered from the region close to Neptune onto an eccentric orbit has a 20-30% chance of obtaining an orbit similar to that of Planet Nine after 4.6Gyr. Our simulations also result in strong or partial clustering of the planetesimals; however, whether or not this clustering is observable depends on the location of the inner edge of the planetesimal belt. If the inner edge is located at 200 au, the degree of clustering amongst observable objects is significant.

[Roger E. Moore]

https://arxiv.org/abs/1807.06783

The Contribution of Dwarf Planets to the Origin of Low Inclination Comets by the Replenishment of Mean Motion Resonances in Debris Disks

Marco A. Muñoz-Gutiérrez, Antonio Peimbert, Bárbara Pichardo
(Submitted on 18 Jul 2018)

In this work we explore a new dynamical path for the delivery of low-inclination comets. In a configuration formed by an interior giant planet and an exterior massive debris disk, where the mass is accounted for by the 50 largest objects in the disk, the strongest mean motion resonances of the giant, located along the belt, are replenished with new material (test particles) due to the influence of the 50 massive objects. Once in resonance, slow chaotic diffusion stirs the orbital elements of the cometary nuclei enough to encounter the giant and to be scattered by it. When the disk is massive enough, both resonant and non-resonant particles are stirred quickly to encounter the giant and form an scattered disk component, greatly increasing the rate for the delivery of cometary material to the inner part of the system. This mechanism is applicable both to the solar system and extrasolar systems in general. Preliminary results, using a disk as massive as the classical Kuiper belt, indicate that the mechanism here proposed can account for about a tenth of the required injection rate to maintain the population of ecliptic comets in steady state. In a more massive belt of 0.25 M⊕, an estimated rate of around 0.6 new comets per year is found. Such a high rate would pose a serious risk for the habitability of rocky interior planets, yet would resemble the late heavy bombardment that was present in the early solar system.

====================

https://academic.oup.com/mnras/artic...rectedFrom=PDF

Determination of the body of the dwarf planet Haumea from observations of a stellar occultation and photometry data

Kondratyev, B. P.; Kornoukhov, V. S.
08/2018

We develop a new method for solving the inverse geometric problem of reconstructing the form of a triaxial ellipsoid through its projection (limb) on to the image plane. This method is based on a rotation matrix with three special angles that are maximally adapted to restore the ellipsoidal shape when directly using positional observations. The geometric properties of the limb are investigated and the theorem is proved: the area of the limb will be maximal (minimal) when the projection of the rotation axis of the ellipsoid on the image plane coincides with the small (large) axis of this limb. A system of eight equations is deduced for finding the spatial shape of the dwarf planet Haumea, as well as the inclination of its ring and the orbits of the satellites. These equations take into account all information on Haumea's photometry, its limb and ring. For each value of the photometric parameter, we calculate the shape and density of the ellipsoidal Haumea model, and its orientation in relation to the ring and the satellite's orbits. There are limitations from below for the elongation of the model, and from above for its average density. By increasing the photometric parameter, the model deviates more from the Jacobi ellipsoids. We find that the orbits of Hi'iaka as well as Haumea's ring do not coincide with Haumea's equator, and that both satellites have prograde motion. The most probable characteristics of the Haumea system are obtained and our results are compared with the results of other researchers.

[Roger E. Moore]

https://www.washingtonpost.com/natio...=.d15d5a46faac

Is there a mysterious Planet Nine lurking in our solar system beyond Neptune? Planet Nine from outer space

Astronomers say they have evidence of a ninth planet in our solar system.

By Charlie Wood
September 2 at 9:00 AM

Many astronomers remain convinced a once-in-a-generation discovery is in the offing — one that would rewrite textbooks down to the elementary school level. “Every time we take a picture,” said Surhud More, an astronomer at the University of Tokyo, “there is this possibility that Planet Nine exists in the shot.” Circumstantial evidence continues to accumulate for the existence of Planet Nine, the hypothetical body thought to be lurking in our solar system far beyond Neptune. But no telescope has been able to spot it. Michael Brown, an astronomer at the California Institute of Technology, says he feels “eternally optimistic” that someone will soon find it, but there’s reason to believe that Planet Nine, if it exists, might be essentially invisible to existing observatories.

[Roger E. Moore]

https://arxiv.org/abs/1805.01203

A new approach to distant solar system object detection in large survey data sets

V. Perdelwitz, M. Völschow, H. M. Müller
(Submitted on 3 May 2018)

The recently postulated existence of a giant ninth planet in our solar system has sparked search efforts for distant solar system objects (SSOs) both via new observations and archival data analysis. Due to the likely faintness of the object in the optical and infrared regime, it has so far eluded detection. We set out to re-analyze data acquired by the Wide-Field Infrared Survey Explorer (WISE), an all-sky survey well suited for the detection of SSOs. We present a new approach to SSO detection via parallactic fitting. Using the heliocentric distance as a fit parameter, our code transforms groups of three or more single observation point sources to heliocentric coordinates under the assumption that all data stem from an object. The fact that the orbit of a distant SSO is approximately linear in heliocentric coordinates over long time-scales can be utilized to produce candidates, which can then be confirmed with follow-up observations. We demonstrate the feasibility of the approach by a posteriori detecting the outer SSO Makemake within WISE data. An all-sky search for Planet Nine yielded no detection. While the postulated Planet Nine eluded detection by our algorithm, we tentatively predict that this new approach to moving-object analysis will enable the discovery of new distant SSOs that cannot be discovered by other algorithms. Especially in cases of sparse data observed over long time spans, our approach is unique and robust due to the use of only one fit parameter.

[Tom Mazanec]

Planet Nine might show up in upcoming CMB observations:
https://www.nextbigfuture.com/2018/0...-planet-9.html

[George]

Planet Nine might show up in upcoming CMB observations:
https://www.nextbigfuture.com/2018/0...-planet-9.html

That’s interesting, but it looks like it might not work if P9 happens to be sliding along in the galactic plane, or am I inferring too much?

[That opening sentence is subject to a little pedantry.]

[Roger E. Moore]

Two papers out today indicate the search for Planet 9 is running aground on statistical rocks. A TNO named Caju (could have been Cujo, okay with me) was cited as evidence of Planet 9 perturbation, but evidence says Caju is an extreme outlier and cannot be relied upon for evidence of Planet 9. Also, from Michael Brown, any idea that orbital resonances of TNOs being used to locate Planet 9 will not work. One gets the idea that new techniques will have to be developed, either statistically or observationally, to find that last planet (or two, or three). Not even going to address the new controversy over whether Pluto is the ninth planet, not gonna go there at all.

==========

https://arxiv.org/abs/1809.02571

A Fruit of a Different Kind: 2015 BP519 as an Outlier among the Extreme Trans-Neptunian Objects

C. de la Fuente Marcos, R. de la Fuente Marcos (Submitted on 7 Sep 2018)

A number of intriguing patterns have been identified in the distributions of the orbital elements of the known extreme trans-Neptunian objects or ETNOs --those with semimajor axis greater than 150 au and perihelion distance greater than 30 au. The announcement of the discovery of 2015 BP519, also known as Caju, has been hailed by some as a consistent piece of robust evidence for the existence of a yet-to-be-discovered massive planet far beyond the trans-Neptunian belt. In this Note, we use the latest data available to provide evidence against 2015 BP519 having followed the same dynamical pathway that placed other ETNOs where they are now. As an statistical outlier within the 29 known ETNOs, 2015 BP519 cannot be used as a reference to further support the trends perhaps present for other ETNOs. Asteroid 2015 BP519 represents a case of extreme dynamical anticorrelation within the ETNO orbital realm and the value of the distance to its descending node, nearly 700 au from the Sun, is the largest of any known ETNO.

==================

https://arxiv.org/abs/1809.02594

Feasibility of a resonance-based Planet Nine search

Elizabeth Bailey, Michael E. Brown, Konstantin Batygin (Submitted on 7 Sep 2018)

It has been proposed that mean motion resonances (MMRs) between Planet Nine and distant objects of the scattered disk might inform the semimajor axis and instantaneous position of Planet Nine. Within the context of this hypothesis, the specific distribution of occupied MMRs largely determines the available constraints. Here we characterize the behavior of scattered Kuiper Belt objects arising in the presence of an eccentric Planet Nine (e 9 ∈ 0.1 , 0.7), focusing on relative sizes of populations occupying particular commensurabilities. Highlighting the challenge of predicting the exact MMR of a given object, we find that the majority of resonant test particles have period ratios with Planet Nine other than those of the form P 9 /P=N/1, N/2 (N∈Z+). Taking into account the updated prior distribution of MMRs outlined in this work, we find that the close spacing of high-order resonances, as well as chaotic transport, preclude resonance-based Planet Nine constraints from current observational data.

[Roger E. Moore]

Last article from the last few days of particular interest, satisfying read begging good questions, BUT... if so many TNO dwarf planets have satellites, why does Ceres have NO satellites? Did Ceres ever have satellites? It's in the asteroid belt, after all, and smaller rocks have moons. Weird.


https://arxiv.org/pdf/1809.02184.pdf

The Albedos, Sizes, Colors and Satellites of Dwarf Planets Compared with Newly Measured Dwarf Planet 2013 FY27

Scott Sheppard, Yanga Fernandez, Arielle Moullet (Submitted on 6 Sep 2018)

2013 FY27 is the ninth intrinsically brightest Trans-Neptunian Object (TNO). We observed 2013 FY27 at thermal wavelengths with ALMA and in the optical with Magellan to determine its size and albedo for the first time and compare it to other dwarf planets. The geometric albedo of 2013 FY27 was found to be 0.17 -0.030+0.045, giving an effective diameter of D = 765 +80-85 km. 2013 FY27 has a size within the transition region between the largest few TNOs that have higher albedos and higher densities than smaller TNOs. No significant short-term optical light curve was found, with variations less than 0.06 mags over hours and days. The Sloan optical colors of 2013 FY27 are g-r=0.76 +-0.02 and r-i=0.31 +-0.03 mags, which is a moderately red color. This color is different than the neutral or ultra-red colors found for the ten largest TNOs, making 2013 FY27 one of the largest known moderately red TNOs, which only start to be seen, and in abundance, at diameters less than 800 km. This suggests something physically different might be associated with TNOs larger than 800 km. It could be that moderately red surfaces are older or less ice rich and TNOs larger than 800 km have fresher surfaces or are able to hold onto more volatile ices. Its also possible TNOs larger than 800 km are more fully differentiated, giving them different surface compositions. A satellite at 0.17 arcsec away and 3.0 +-0.2 mags fainter than 2013 FY27 was found through Hubble Space Telescope observations. Almost all the largest TNOs have satellites, and the relative small size of 2013 FY27's satellite suggests it was created through a direct collision, similar to satellites known around the largest TNOs. Assuming the satellite has a similar albedo as the primary, it is about 190 km in diameter, making the primary D = 740 +85-90 km.

[Roger E. Moore]

Including this report here because it relates directly to the search for "Planet X".


https://arxiv.org/abs/1810.00013

A New High Perihelion Inner Oort Cloud Object

Scott Sheppard, Chadwick Trujillo, David Tholen, Nathan Kaib (Submitted on 28 Sep 2018)

Inner Oort Cloud objects have perihelia beyond the Kuiper Belt with semi-major axes less than a few thousand au. They are beyond the strong gravitational influences of the known planets yet are tightly bound to the Sun such that outside forces minimally affect them. Here we report the discovery of the third known Inner Oort Cloud object after Sedna and 2012 VP113, called 2015 TG387. 2015 TG387 has a perihelion of 65 ± 1 au with a semi-major axis of 1190 ±70 au. The longitude of perihelion angle for 2015 TG387 is between that of Sedna and 2012 VP113, and thus similar to the main group of clustered extreme trans-Neptunian objects (ETNOs), which may be shepherded into similar orbital angles by an unknown massive distant planet, called Planet X or Planet 9. 2015 TG387's orbit is stable over the age of the solar system from the known planets and Galactic tide. When including simulated stellar encounters to our Sun over 4 Gyrs, 2015 TG387's orbit is still mostly stable, but its dynamical evolution depends on the stellar encounter scenarios used. Surprisingly, when including a massive Planet X beyond a few hundred au on an eccentric orbit that is anti-aligned in longitude of perihelion with most of the known ETNOs, we find 2015 TG387 is typically stable for Planet X orbits that render the other ETNOs stable as well. In fact, 2015 TG387's longitude of perihelion librates about 180 degrees from Planet X's longitude of perihelion in most stable simulations, keeping 2015 TG387 anti-aligned with Planet X over the age of the solar system. We find a power law slope near 3 for the semi-major axis distribution of Inner Oort Cloud objects (IOCs), meaning there are many more high than low semi-major axis IOCs. There are about 2 million IOCs larger than 40 km, giving a mass of 10^22 kg. The IOCs inclination distribution is similar to the scattered disk, with an average inclination of 19 degs.

QUOTES: Extreme Trans-Neptunian objects (ETNOs) have perihelia well beyond Neptune and large semi-major axes (a > 150 − 250 au). The ETNOs have only minimal interactions with the known giant 2 planets and thus are strongly sensitive to gravitational forces hundreds to thousands of au from the Sun. Thus, the ETNOs can be used to probe the solar system beyond the Kuiper Belt (Trujillo and Sheppard 2014).

The ETNOs can be separated into three sub-classes (Figure 1). The scattered ETNOs have perihelia below 38-45 au and likely were created from gravitational scattering with Neptune and still have some significant interactions with Neptune (Brasser & Schwamb 2015). The detached ETNOs have perihelia between about 40-45 to 50-60 au and likely have minimal interactions with the giant planets, but are still relatively close to Neptune and thus could still have significant interactions with the known giant planets (Gladman et al. 2002; Bannister et al. 2017). Inner Oort Cloud objects (IOCs) have perihelia greater than 50-60 au and are too far from the giant planets to be strongly influenced by them (Gomes et al. 2008).

...2015 TG387 is the first detached ETNO or inner Oort cloud object to have an argument of perihelion closer to 180 as opposed to 0 degrees.... 2015 TG387 continues the longitude clustering trend seen for the inner Oort cloud objects and ETNOs, which might be caused by a massive planet shepherding these objects.

...This is surprising to find that the third known inner Oort cloud object is stable with the distant massive planet orbits found for the other inner Oort cloud objects and ETNOs, and not only is 2015 TG387 stable, but it has resonance behavior with its longitude of perihelion, librating 180 degrees from the planet’s. Though this does not prove the hypothetical distant planet first realized by Trujillo and Sheppard (2014) and further revealed by Batygin and Brown (2016a) is real, it is strongly suggestive.

[Roger E. Moore]

Just-out news story relating to the ETNO above, TG387 - "The Goblin" apparently.


‘The Goblin’: New Distant Dwarf Planet Bolsters Evidence for Planet X

By Nathaniel Scharping | October 2, 2018 9:00 am

http://blogs.discovermagazine.com/d-.../#.W7ONRLuWzIU

[grapes]

Last article from the last few days of particular interest, satisfying read begging good questions, BUT... if so many TNO dwarf planets have satellites, why does Ceres have NO satellites? Did Ceres ever have satellites? It's in the asteroid belt, after all, and smaller rocks have moons. Weird.

Maybe they just haven't found them yet!

[George]

Maybe they just haven't found them yet!

Wouldn't Jupiter spoil any long-lasting satellite orbit for dwarfs in the asteroid belt?