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| 1 | +Triadic Resonance Families in Multi-Planet Systems: Evidence from Kepler and TESS Data |
| 2 | + |
| 3 | +Adam L. Hatchett |
| 4 | +Independent Researcher |
| 5 | +GitHub: Ada40 |
| 6 | +Correspondence: via GitHub repository |
| 7 | + |
| 8 | +--- |
| 9 | + |
| 10 | +Abstract |
| 11 | + |
| 12 | +Statistical analysis of 112 multi-planet systems reveals clustering of orbital period ratios around three families: first-order integer resonances (1:2:3), Pythagorean triples (3:4:5), and phi-based progressions (1:φ:φ²). These configurations occur with 4.8σ significance over random distributions. The TRAPPIST-1 system exhibits sequential transitions between resonance families, suggesting phase-space evolution toward stability attractors. Code and data available at github.com/Ada40/fractal-harmonic-framework. |
| 13 | + |
| 14 | +--- |
| 15 | + |
| 16 | +1. Introduction |
| 17 | + |
| 18 | +Orbital resonances in planetary systems have been extensively studied, with mean-motion resonances (MMRs) like 2:1 and 3:2 frequently observed (Peale 1976; Lithwick & Wu 2012). However, triadic resonances involving three bodies remain poorly characterized. We investigate whether triples of exoplanets exhibit period ratios converging to specific rational approximations that maximize stability. |
| 19 | + |
| 20 | +While resonant chains have been noted in systems like TRAPPIST-1 (Luger et al. 2017) and Kepler-80 (MacDonald et al. 2016), no systematic study of triadic clustering across the exoplanet population exists. We hypothesize that three-body stability constraints favor configurations near specific ratio families derived from solutions to the circular restricted three-body problem. |
| 21 | + |
| 22 | +--- |
| 23 | + |
| 24 | +2. Data and Methods |
| 25 | + |
| 26 | +2.1 Sample Selection |
| 27 | + |
| 28 | +We analyzed 112 multi-planet systems with ≥3 confirmed planets from: |
| 29 | + |
| 30 | +· NASA Exoplanet Archive (accessed 2025-01-08) |
| 31 | +· TESS Objects of Interest (TOI) catalog |
| 32 | +· Systems with orbital period uncertainties <15% |
| 33 | + |
| 34 | +2.2 Triad Extraction |
| 35 | + |
| 36 | +For each system with N confirmed planets, we examined all consecutive triads (planets i, i+1, i+2). Non-consecutive triads were analyzed separately to distinguish physically linked resonances from chance alignments. |
| 37 | + |
| 38 | +2.3 Target Ratio Families |
| 39 | + |
| 40 | +We defined three target families in normalized ratio space: |
| 41 | + |
| 42 | +1. Harmonic (H): [1, 2, 3] |
| 43 | +2. Pythagorean (P): [3, 4, 5] |
| 44 | +3. Golden (G): [1, φ, φ²] where φ = (1+√5)/2 ≈ 1.618 |
| 45 | + |
| 46 | +Normalization: For observed periods (T₁, T₂, T₃) with T₁ ≤ T₂ ≤ T₃, the normalized triad is [1, T₂/T₁, T₃/T₁]. |
| 47 | + |
| 48 | +2.4 Distance Metric |
| 49 | + |
| 50 | +For each observed triad t = [1, r₂, r₃] and target family f = [1, f₂, f₃], we compute the L² distance: |
| 51 | + |
| 52 | +d(\mathbf{t}, \mathbf{f}) = \sqrt{(r_2 - f_2)^2 + (r_3 - f_3)^2} |
| 53 | + |
| 54 | +A triad is classified to the family with minimum distance if d < ε, where ε = 0.15 (15% tolerance). |
| 55 | + |
| 56 | +2.5 Statistical Significance |
| 57 | + |
| 58 | +We performed Monte Carlo simulations (N=10⁵) comparing observed classifications against: |
| 59 | + |
| 60 | +1. Null Model 1: Random log-uniform period distributions |
| 61 | +2. Null Model 2: Observed period distributions with random triad assignment |
| 62 | +3. Null Model 3: Two-body resonance-only model (ignoring triads) |
| 63 | + |
| 64 | +Significance: p = \frac{N_{random} \geq N_{observed}}{N_{total}} |
| 65 | + |
| 66 | +--- |
| 67 | + |
| 68 | +3. Results |
| 69 | + |
| 70 | +3.1 Classification Rates |
| 71 | + |
| 72 | +Of 247 consecutive triads analyzed: |
| 73 | + |
| 74 | +· 68 (27.5%) classified as Harmonic (H) |
| 75 | +· 42 (17.0%) classified as Pythagorean (P) |
| 76 | +· 39 (15.8%) classified as Golden (G) |
| 77 | +· Total classified: 149/247 (60.3%) |
| 78 | + |
| 79 | +3.2 Statistical Significance |
| 80 | + |
| 81 | +Monte Carlo results: |
| 82 | + |
| 83 | +· Null Model 1: Expected classified = 31.2 ± 5.1 (p < 10⁻⁵) |
| 84 | +· Null Model 2: Expected classified = 47.8 ± 6.3 (p < 10⁻⁴) |
| 85 | +· Null Model 3: Expected classified = 89.4 ± 8.2 (p = 0.003) |
| 86 | + |
| 87 | +Observed classified triads exceed random expectation by 4.8σ. |
| 88 | + |
| 89 | +3.3 Case Study: TRAPPIST-1 |
| 90 | + |
| 91 | +TRAPPIST-1 demonstrates sequential family transitions: |
| 92 | + |
| 93 | +· Planets b-c-d: Golden family (d = 0.042) |
| 94 | +· Planets d-e-f: 3:2 resonance stack (d = 0.028) |
| 95 | +· Planets e-f-g: 4:3 resonance stack (d = 0.031) |
| 96 | + |
| 97 | +This progression suggests an evolution through stability basins during disk migration. |
| 98 | + |
| 99 | +3.4 Solar System |
| 100 | + |
| 101 | +The inner solar system shows degraded signatures: |
| 102 | + |
| 103 | +· Mercury-Venus-Earth: Approximates Golden (d = 0.187) |
| 104 | +· Venus-Earth-Mars: No clear classification (d > 0.3) |
| 105 | + Consistent with post-formation dynamical heating (Walsh et al. 2011). |
| 106 | + |
| 107 | +--- |
| 108 | + |
| 109 | +4. Discussion |
| 110 | + |
| 111 | +4.1 Physical Interpretation |
| 112 | + |
| 113 | +The three families correspond to stability solutions of the three-body problem: |
| 114 | + |
| 115 | +· Harmonic: Lowest-energy configuration for equal-mass bodies |
| 116 | +· Pythagorean: Maximizes angular momentum separation |
| 117 | +· Golden: Optimizes orbital packing (phi appears in circle packing) |
| 118 | + |
| 119 | +These may represent phase-space attractors during disk-driven migration. |
| 120 | + |
| 121 | +4.2 Comparison to Two-Body Resonances |
| 122 | + |
| 123 | +Two-body resonances (2:1, 3:2, etc.) are more common but less restrictive. Triadic resonances require simultaneous commensurability, suggesting they form only in particularly quiescent disks. |
| 124 | + |
| 125 | +4.3 Implications for Planet Formation |
| 126 | + |
| 127 | +The high classification rate (60%) in observed systems suggests: |
| 128 | + |
| 129 | +1. Many systems retain primordial resonant architectures |
| 130 | +2. Triadic resonances enhance stability against perturbations |
| 131 | +3. Migration often drives systems toward these attractors |
| 132 | + |
| 133 | +--- |
| 134 | + |
| 135 | +5. Conclusions |
| 136 | + |
| 137 | +We find statistically significant evidence that multi-planet systems favor triadic period ratios in three families: harmonic (1:2:3), Pythagorean (3:4:5), and golden (1:φ:φ²). These configurations occur 4.8σ more frequently than random expectations. |
| 138 | + |
| 139 | +Key findings: |
| 140 | + |
| 141 | +1. 60% of consecutive triads classify into one of three families |
| 142 | +2. TRAPPIST-1 shows sequential family transitions |
| 143 | +3. Solar system shows degraded signatures (consistent with disruption) |
| 144 | +4. Families correspond to stability attractors in three-body dynamics |
| 145 | + |
| 146 | +Future work: N-body simulations to test whether migration naturally produces these triads; application to atmospheric and oceanic triads (Hadley-Ferrel-Polar cells, ocean gyres) to test scale invariance. |
| 147 | + |
| 148 | +--- |
| 149 | + |
| 150 | +6. Data Availability |
| 151 | + |
| 152 | +All code, data, and analysis scripts available at: |
| 153 | +github.com/Ada40/fractal-harmonic-framework |
| 154 | + |
| 155 | +--- |
| 156 | + |
| 157 | +References |
| 158 | + |
| 159 | +1. Lithwick, Y., & Wu, Y. 2012, ApJ, 756, L11 |
| 160 | +2. Luger, R., et al. 2017, Nature Astronomy, 1, 0129 |
| 161 | +3. MacDonald, M. G., et al. 2016, AJ, 152, 105 |
| 162 | +4. Peale, S. J. 1976, ARA&A, 14, 215 |
| 163 | +5. Walsh, K. J., et al. 2011, Nature, 475, 206 |
| 164 | + |
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