1
|
Smullen RA, Volk K. Machine Learning Classification of Kuiper Belt Populations. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 2020; 497:1391-1403. [PMID: 33293736 PMCID: PMC7720433 DOI: 10.1093/mnras/staa1935] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
In the outer solar system, the Kuiper Belt contains dynamical sub-populations sculpted by a combination of planet formation and migration and gravitational perturbations from the present-day giant planet configuration. The subdivision of observed Kuiper Belt objects (KBOs) into Different dynamical classes is based on their current orbital evolution in numerical integrations of their orbits. Here we demonstrate that machine learning algorithms are a promising tool for reducing both the computational time and human effort required for this classification. Using a Gradient Boosting Classifier, a type of machine learning regression tree classifier trained on features derived from short numerical simulations, we sort observed KBOs into four broad, dynamically distinct populations-classical, resonant, detached, and scattering- with a >97 per cent accuracy for the testing set of 542 securely classified KBOs. Over 80 per cent of these objects have a > 3σ probability of class membership, indicating that the machine learning method is classifying based on the fundamental dynamical features of each population. We also demonstrate how, by using computational savings over traditional methods, we can quickly derive a distribution of class membership by examining an ensemble of object clones drawn from the observational errors. We find two major reasons for misclassification: inherent ambiguity in the orbit of the object-for instance, an object that is on the edge of resonance-and a lack of representative examples in the training set. This work provides a promising avenue to explore for fast and accurate classification of the thousands of new KBOs expected to be found by surveys in the coming decade.
Collapse
Affiliation(s)
- Rachel A. Smullen
- Department of Astronomy, University of Arizona, 933 N Cherry Ave., Tucson 85719 USA
| | - Kathryn Volk
- Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Blvd., Tucson 85719 USA
| |
Collapse
|
2
|
Scholtz J, Unwin J. What If Planet 9 Is a Primordial Black Hole? PHYSICAL REVIEW LETTERS 2020; 125:051103. [PMID: 32794880 DOI: 10.1103/physrevlett.125.051103] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 02/10/2020] [Accepted: 06/26/2020] [Indexed: 06/11/2023]
Abstract
We highlight that the anomalous orbits of trans-Neptunian objects (TNOs) and an excess in microlensing events in the 5-year Optical Gravitational Lensing Experiment data set can be simultaneously explained by a new population of astrophysical bodies with mass several times that of the Earth (M_{⊕}). We take these objects to be primordial black holes (PBHs) and point out the orbits of TNOs would be altered if one of these PBHs was captured by the Solar System, inline with the Planet 9 hypothesis. Capture of a free floating planet is a leading explanation for the origin of Planet 9, and we show that the probability of capturing a PBH instead is comparable. The observational constraints on a PBH in the outer Solar System significantly differ from the case of a new ninth planet. This scenario could be confirmed through annihilation signals from the dark matter microhalo around the PBH.
Collapse
Affiliation(s)
- Jakub Scholtz
- Institute for Particle Physics Phenomenology, Durham University, Durham DH1 3LE, United Kingdom
| | - James Unwin
- Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60607, USA and Department of Physics, University of California, Berkeley and Theoretical Physics Group, LBNL and Mathematics Sciences Research Institute, Berkeley, California 94720, USA
| |
Collapse
|
3
|
Organic Components of Small Bodies in the Outer Solar System: Some Results of the New Horizons Mission. Life (Basel) 2020; 10:life10080126. [PMID: 32731390 PMCID: PMC7460487 DOI: 10.3390/life10080126] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 07/18/2020] [Accepted: 07/24/2020] [Indexed: 11/21/2022] Open
Abstract
The close encounters of the Pluto–Charon system and the Kuiper Belt object Arrokoth (formerly 2014 MU69) by NASA’s New Horizons spacecraft in 2015 and 2019, respectively, have given new perspectives on the most distant planetary bodies yet explored. These bodies are key indicators of the composition, chemistry, and dynamics of the outer regions of the Solar System’s nascent environment. Pluto and Charon reveal characteristics of the largest Kuiper Belt objects formed in the dynamically evolving solar nebula inward of ~30 AU, while the much smaller Arrokoth is a largely undisturbed relic of accretion at ~45 AU. The surfaces of Pluto and Charon are covered with volatile and refractory ices and organic components, and have been shaped by geological activity. On Pluto, N2, CO and CH4 are exchanged between the atmosphere and surface as gaseous and condensed phases on diurnal, seasonal and longer timescales, while Charon’s surface is primarily inert H2O ice with an ammoniated component and a polar region colored with a macromolecular organic deposit. Arrokoth is revealed as a fused binary body in a relatively benign space environment where it originated and has remained for the age of the Solar System. Its surface is a mix of CH3OH ice, a red-orange pigment of presumed complex organic material, and possibly other undetected components.
Collapse
|
4
|
Rubin M, Engrand C, Snodgrass C, Weissman P, Altwegg K, Busemann H, Morbidelli A, Mumma M. On the Origin and Evolution of the Material in 67P/Churyumov-Gerasimenko. SPACE SCIENCE REVIEWS 2020. [PMID: 32801398 DOI: 10.1007/s11214-019-0625-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Primitive objects like comets hold important information on the material that formed our solar system. Several comets have been visited by spacecraft and many more have been observed through Earth- and space-based telescopes. Still our understanding remains limited. Molecular abundances in comets have been shown to be similar to interstellar ices and thus indicate that common processes and conditions were involved in their formation. The samples returned by the Stardust mission to comet Wild 2 showed that the bulk refractory material was processed by high temperatures in the vicinity of the early sun. The recent Rosetta mission acquired a wealth of new data on the composition of comet 67P/Churyumov-Gerasimenko (hereafter 67P/C-G) and complemented earlier observations of other comets. The isotopic, elemental, and molecular abundances of the volatile, semi-volatile, and refractory phases brought many new insights into the origin and processing of the incorporated material. The emerging picture after Rosetta is that at least part of the volatile material was formed before the solar system and that cometary nuclei agglomerated over a wide range of heliocentric distances, different from where they are found today. Deviations from bulk solar system abundances indicate that the material was not fully homogenized at the location of comet formation, despite the radial mixing implied by the Stardust results. Post-formation evolution of the material might play an important role, which further complicates the picture. This paper discusses these major findings of the Rosetta mission with respect to the origin of the material and puts them in the context of what we know from other comets and solar system objects.
Collapse
Affiliation(s)
- Martin Rubin
- Physikalisches Institut, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland
| | - Cécile Engrand
- CNRS/IN2P3, IJCLab, Université Paris-Saclay, 91405 Orsay Cedex, France
| | - Colin Snodgrass
- Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, EH9 3HJ UK
| | | | - Kathrin Altwegg
- Physikalisches Institut, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland
| | - Henner Busemann
- Institute of Geochemistry and Petrology, Department of Earth Sciences, ETH Zurich, Zurich, Switzerland
| | | | - Michael Mumma
- NASA Goddard Space Flight Center, 8800 Greenbelt Rd., Greenbelt, 20771 MD USA
| |
Collapse
|
5
|
|
6
|
Not a simple relationship between Neptune's migration speed and Kuiper belt inclination excitation. ACTA ACUST UNITED AC 2019; 158. [PMID: 31631895 DOI: 10.3847/1538-3881/ab2639] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We present numerical simulations of giant planet migration in our solar system and examine how the speed of planetary migration affects inclinations in the resulting population of small bodies (test particles) scattered outward and subsequently captured into Neptune's 3:2 mean motion resonance (the Plutinos) as well as the hot classical Kuiper belt population. We do not find a consistent relationship between the degree of test particle inclination excitation and e-folding planet migration timescales in the range 5 - 50 Myr. Our results present a counter-example to Nesvorný (2015)'s finding that the Plutino and hot classical inclinations showed a marked increase with increasing e-folding timescales for Neptune's migration. We argue that these differing results are likely due to differing secular architectures of the giant planets during and after migration. Small changes in the planets' initial conditions and differences in the numerical implementation of planet migration can result in different amplitudes of the planets' inclination secular modes, and this can lead to different final inclination distributions for test particles in the simulations. We conclude that the observed large inclination dispersion of Kuiper belt objects does not require Neptune's migration to be slow; planetary migration with e-folding timescales of 5, 10, 30, and 50 Myr can all yield inclination dispersions similar to the observed Plutino and hot classical populations, with no correlation between the degree of inclination excitation and migration speed.
Collapse
|
7
|
Kaib NA, Pike R, Lawler S, Kovalik M, Brown C, Alexandersen M, Bannister MT, Gladman BJ, Petit JM. OSSOS XV: PROBING THE DISTANT SOLAR SYSTEM WITH OBSERVED SCATTERING TNOS. THE ASTRONOMICAL JOURNAL 2019; 158:43. [PMID: 31379385 PMCID: PMC6677154 DOI: 10.3847/1538-3881/ab2383] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Most known trans-Neptunian objects (TNOs) gravitationally scattering off the giant planets have orbital inclinations consistent with an origin from the classical Kuiper belt, but a small fraction of these "scattering TNOs" have inclinations that are far too large (i > 45°) for this origin. These scattering outliers have previously been proposed to be interlopers from the Oort cloud or evidence of an undiscovered planet. Here we test these hypotheses using N-body simulations and the 69 centaurs and scattering TNOs detected in the Outer Solar Systems Origins Survey and its predecessors. We confirm that observed scattering objects cannot solely originate from the classical Kuiper belt, and we show that both the Oort cloud and a distant planet generate observable highly inclined scatterers. Although the number of highly inclined scatterers from the Oort Cloud is ~3 times less than observed, Oort cloud enrichment from the Sun's galactic migration or birth cluster could resolve this. Meanwhile, a distant, low-eccentricity 5 M⊕ planet replicates the observed fraction of highly inclined scatterers, but the overall inclination distribution is more excited than observed. Furthermore, the distant planet generates a longitudinal asymmetry among detached TNOs that is less extreme than often presumed, and its direction reverses across the perihelion range spanned by known TNOs. More complete models that explore the dynamical origins of the planet are necessary to further study these features. With observational biases well-characterized, our work shows that the orbital distribution of detected scattering bodies is a powerful constraint on the unobserved distant solar system.
Collapse
Affiliation(s)
- Nathan A Kaib
- HL Dodge Department of Physics & Astronomy, University of Oklahoma, Norman, OK 73019, USA
| | - Rosemary Pike
- Institute of Astronomy and Astrophysics, Academia Sinica; 11F of AS/NTU Astronomy-Mathematics Building, No. 1 Roosevelt Rd., Sec. 4, Taipei 10617, Taiwan
| | - Samantha Lawler
- Herzberg Astronomy and Astrophysics Research Centre, National Research Council of Canada, 5071 West Saanich Rd, Victoria, British Columbia V9E 2E7, Canada
| | - Maya Kovalik
- Computer Science, Engineering, and Physics Department, University of Mary Hardin-Baylor, Belton, TX 76513, USA
| | - Christopher Brown
- HL Dodge Department of Physics & Astronomy, University of Oklahoma, Norman, OK 73019, USA
| | - Mike Alexandersen
- Institute of Astronomy and Astrophysics, Academia Sinica; 11F of AS/NTU Astronomy-Mathematics Building, No. 1 Roosevelt Rd., Sec. 4, Taipei 10617, Taiwan
| | - Michele T Bannister
- Astrophysics Research Centre, Queen's University Belfast, Belfast BT7 1NN, United Kingdom
| | - Brett J Gladman
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - Jean-Marc Petit
- Institut UTINAM UMR6213, CNRS, Univ. Bourgogne Franche-Comt, OSU Theta F-25000 Besançon, France
| |
Collapse
|
8
|
Quillen AC, Chen YY, Noyelles B, Loane S. Tilting Styx and Nix but not Uranus with a Spin-Precession-Mean-motion resonance. CELESTIAL MECHANICS AND DYNAMICAL ASTRONOMY 2018; 130:11. [PMID: 32924029 PMCID: PMC7485118 DOI: 10.1007/s10569-017-9804-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 10/23/2017] [Accepted: 10/27/2017] [Indexed: 06/11/2023]
Abstract
A Hamiltonian model is constructed for the spin axis of a planet perturbed by a nearby planet with both planets in orbit about a star. We expand the planet-planet gravitational potential perturbation to first order in orbital inclinations and eccentricities, finding terms describing spin resonances involving the spin precession rate and the two planetary mean motions. Convergent planetary migration allows the spinning planet to be captured into spin resonance. With initial obliquity near zero, the spin resonance can lift the planet's obliquity to near 90 or 180 degrees depending upon whether the spin resonance is first or zero-th order in inclination. Past capture of Uranus into such a spin resonance could give an alternative non-collisional scenario accounting for Uranus's high obliquity. However we find that the time spent in spin resonance must be so long that this scenario cannot be responsible for Uranus's high obliquity. Our model can be used to study spin resonance in satellite systems. Our Hamiltonian model explains how Styx and Nix can be tilted to high obliquity via outward migration of Charon, a phenomenon previously seen in numerical simulations.
Collapse
Affiliation(s)
- Alice C Quillen
- Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 USA
- Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China
| | - Yuan-Yuan Chen
- Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 USA
- Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China
| | - Benoît Noyelles
- Department of Mathematics and the Namur Centre for Complex Systems (naXys), University of Namur, 8 Rempart de la Vierge, Namur B-5000 Belgium
| | - Santiago Loane
- Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 USA
| |
Collapse
|
9
|
|