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1. Can Neptune’s Distant Mean Motion Resonances Constrain Undiscovered Planets in the Solar System? Lessons from a Case Study of the 9:1 Resonance

   https://doi.org/10.3847/PSJ/ad2201  

   Porter, Matthew W. ; Gerdes, David W. ; Napier, Kevin J. ; Lin 林, Hsing Wen 省文 ; Adams, Fred C. ( March 2024 , The Planetary Science Journal)

   Recent observational surveys of the outer solar system provide evidence that Neptune's distantn:1 mean motion resonances may harbor relatively large reservoirs of trans-Neptunian objects (TNOs). In particular, the discovery of two securely classified 9:1 resonators, 2015 KE₁₇₂and 2007 TC₄₃₄, by the Outer Solar System Origins Survey is consistent with a population of order 10⁴such objects in the 9:1 resonance with absolute magnitudeH_r< 8.66. This work investigates whether the long-term stability of such populations in Neptune’sn:1 resonances can be used to constrain the existence of distant 5–10M_⊕planets orbiting at hundreds of au. The existence of such a planet has been proposed to explain a reported clustering in the orbits of highly eccentric “extreme” trans-Neptunian objects (or eTNOs), although this hypothesis remains controversial. We engage in a focused computational case study of the 9:1 resonance, generating synthetic populations and integrating them for 1 Gyr in the presence of 81 different test planets with various masses, perihelion distances, eccentricities, and inclinations. While none of the tested planets are incompatible with the existence of 9:1 resonators, our integrations shed light on the character of the interaction between such planets and nearbyn:1 resonances, and we use this knowledge to construct a simple heuristic method for determining whether or not a given planet could destabilize a given resonant population. We apply this method to the currently estimated properties of Planet 9, and find that a large primordial population in the 15:1 resonance (or beyond), if discovered in the future, could potentially constrain the existence of this planet.

    

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2. Orbital Dynamics Landscape near the Most Distant Known Trans-Neptunian Objects

   https://doi.org/10.3847/1538-4357/ac866b  

   Volk, Kathryn ; Malhotra, Renu ( October 2022 , The Astrophysical Journal)

   The most distant known trans-Neptunian objects (TNOs), those with perihelion distance above 38 au and semimajor axis above 150 au, are of interest for their potential to reveal past, external, or present but unseen perturbers. Realizing this potential requires understanding how the known planets influence their orbital dynamics. We use a recently developed Poincaré mapping approach for orbital phase space studies of the circular planar restricted three-body problem, which we have extended to the case of the 3D restricted problem withNplanetary perturbers. With this approach, we explore the dynamical landscape of the 23 most distant TNOs under the perturbations of the known giant planets. We find that, counter to common expectations, almost none of these TNOs are far removed from Neptune’s resonances. Nearly half (11) of these TNOs have orbits consistent with stable libration in Neptune’s resonances; in particular, the orbits of TNOs 148209 and 474640 overlap with Neptune’s 20:1 and 36:1 resonances, respectively. Five objects can be ruled currently nonresonant, despite their large orbital uncertainties, because our mapping approach determines the resonance boundaries in angular phase space in addition to semimajor axis. Only three objects are in orbital regions not appreciably affected by resonances: Sedna, 2012 VP113 and 2015 KG163. Our analysis also demonstrates that Neptune’s resonances impart a modest (few percent) nonuniformity in the longitude of perihelion distribution of the currently observable distant TNOs. While not large enough to explain the observed clustering, this small dynamical sculpting of the perihelion longitudes could become relevant for future, larger TNO data sets.

    

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3. OSSOS XXV: Large Populations and Scattering–Sticking in the Distant Trans-Neptunian Resonances

   https://doi.org/10.3847/PSJ/ac67e0  

   Crompvoets, B. L. ; Lawler, S. M. ; Volk, K. ; Chen, Y.-T. ; Gladman, B. ; Peltier, L. ; Alexandersen, M. ; Bannister, M. T. ; Gwyn, S. ; Kavelaars, J. J. ; et al ( May 2022 , The Planetary Science Journal)

   Abstract There have been 77 TNOs discovered to be librating in the distant trans-Neptunian resonances (beyond the 2:1 resonance, at semimajor axes greater than 47.7 au) in four well-characterized surveys: the Outer Solar System Origins Survey (OSSOS) and three similar prior surveys. Here, we use the OSSOS Survey Simulator to measure their intrinsic orbital distributions using an empirical parameterized model. Because many of the resonances had only one or very few detections, j : k resonant objects were grouped by k in order to have a better basis for comparison between models and reality. We also use the Survey Simulator to constrain their absolute populations, finding that they are much larger than predicted by any published Neptune migration model to date; we also find population ratios that are inconsistent with published models, presenting a challenge for future Kuiper Belt emplacement models. The estimated population ratios between these resonances are largely consistent with scattering–sticking predictions, though further discoveries of resonant TNOs with high-precision orbits will be needed to determine whether scattering–sticking can explain the entire distant resonant population or not. 

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4. Gravitational Wave Sources in Our Galactic Backyard: Predictions for BHBH, BHNS, and NSNS Binaries Detectable with LISA

   https://doi.org/10.3847/1538-4357/ac8675  

   Wagg, T. ; Broekgaarden, F. S. ; de Mink, S. E. ; Frankel, N. ; van Son, L. A. C. ; Justham, S. ( October 2022 , The Astrophysical Journal)

   Future searches for gravitational waves from space will be sensitive to double compact objects in our Milky Way. We present new simulations of the populations of double black holes (BHBHs), BH neutron stars (BHNSs), and double neutron stars (NSNSs) that will be detectable by the planned space-based gravitational-wave detector called Laser Interferometer Space Antenna (LISA). For our estimates, we use an empirically informed model of the metallicity-dependent star formation history of the Milky Way. We populate it using an extensive suite of binary population-synthesis predictions for varying assumptions relating to mass transfer, common-envelope, supernova kicks, remnant masses, and wind mass-loss physics. For a 4(10) yr LISA mission, we predict between 30–370(50–550) detections over these variations, out of which 6–154 (9–238) are BHBHs, 2–198 (3–289) are BHNSs, and 3–35 (4–57) are NSNSs. We expect that about 50% (60%) can be distinguished from double white dwarf sources based on their mass or eccentricity and localization. Specifically, for about 10% (15%), we expect to be able to determine chirp masses better than 10%. For 13% (13%), we expect sky-localizations better than 1°. We discuss how the variations in the physics assumptions alter the distribution of properties of the detectable systems, even when the detection rates are unchanged. We further discuss the possibility of multimessenger observations of pulsar populations with the Square Kilometre Array and assess the benefits of extending the LISA mission.

    

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5. Col-OSSOS: Probing Ice Line/Color Transitions within the Kuiper Belt’s Progenitor Populations

   https://doi.org/10.3847/PSJ/ac42c9  

   Buchanan, Laura E. ; Schwamb, Megan E. ; Fraser, Wesley C. ; Bannister, Michele T. ; Marsset, Michaël ; Pike, Rosemary E. ; Nesvorný, David ; Kavelaars, J. J. ; Benecchi, Susan D. ; Lehner, Matthew J. ; et al ( January 2022 , The Planetary Science Journal)

   Dynamically excited objects within the Kuiper Belt show a bimodal distribution in their surface colors, and these differing surface colors may be a tracer of where these objects formed. In this work, we explore radial color distributions in the primordial planetesimal disk and implications for the positions of ice line/color transitions within the Kuiper Belt’s progenitor populations. We combine a full dynamical model of the Kuiper Belt’s evolution due to Neptune’s migration with precise surface colors measured by the Colours of the Outer Solar System Origins Survey in order to examine the true color ratios within the Kuiper Belt and the ice lines within the primordial disk. We investigate the position of a dominant, surface color–changing ice line, with two possible surface color layouts within the initial disk: (1) inner neutral surfaces and outer red and (2) inner red surfaces and outer neutral. We performed simulations with a primordial disk that truncates at 30 au. By radially stepping the color transition out through 0.5 au intervals, we show that both disk configurations are consistent with the observed color fraction. For an inner neutral, outer red primordial disk, we find that the color transition can be at${28}_{-3}^{+2}$au at a 95% confidence level. For an inner red, outer neutral primordial disk, the color transition can be at${27}_{-3}^{+3}$au at a 95% confidence level.

    

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