Kepler & NotEasy
NotEasy NotEasy
Kepler, I've been staring at how chaotic zones form around resonant exoplanets—want to dissect that map and see if any hidden patterns emerge without skimping on the math?
Kepler Kepler
Sure thing, let’s pull up a map of the resonance zones. First we’ll label the mean‑motion resonances—like 2:1, 3:2, 4:3—and note their locations in semi‑major axis. Then we can plot the width of each resonance using the standard formula Δa ≈ a (μ/3)¹/³, where μ is the planet‑star mass ratio. Once we have those widths, we’ll check for overlap by seeing where Δa₁ + Δa₂ exceeds the distance between the resonances; that’s where chaos sets in. If you want the math laid out, just tell me which system we’re looking at and I’ll crunch the numbers.
NotEasy NotEasy
Alright, pick a system and we’ll see how much chaos the math can squeeze out of it.
Kepler Kepler
Let’s pick TRAPPIST‑1. It has seven Earth‑size planets, many in tight resonances. For each planet we calculate the resonant width using Δa ≈ a (μ/3)¹/³. Because the planets are so close, the widths overlap a lot. The 4:3, 3:2, and 2:1 resonances crowd the inner system, so the chaos border lies just beyond planet f. If we run the formula for each pair, we’ll see that the chaotic zone extends roughly from 0.02 AU out to 0.1 AU, basically covering planets b through e. The math tells us the overlap is enough that a small perturbation can push an orbit into a chaotic path, especially for the innermost bodies. Want me to pull up the exact numbers for each resonance?
NotEasy NotEasy
Sure, here’s a quick rundown: for TRAPPIST‑1 b (a≈0.011 AU) μ≈3×10⁻⁵ so Δa≈0.0006 AU, for c (0.015 AU) Δa≈0.0008 AU, d (0.021 AU) Δa≈0.0011 AU, e (0.028 AU) Δa≈0.0014 AU, f (0.037 AU) Δa≈0.0018 AU, g (0.045 AU) Δa≈0.0021 AU, h (0.059 AU) Δa≈0.0026 AU. The gaps between the 4:3, 3:2, and 2:1 chain are smaller than the sum of adjacent Δa’s, so overlap starts around f and extends past h. A tweak of a few percent in any of those widths could shift the chaos border a few thousandths of an AU. If you need the exact arithmetic, just let me know.
Kepler Kepler
That’s a solid run‑through, thanks for the numbers. With those widths the resonance overlap region really does look like a thick “traffic jam” from b to h. A tiny change in the mass ratio or a slight shift in orbital spacing could open up a small corridor of stability or, conversely, tighten the chaos. If you’re curious, we could run a quick N‑body simulation just to see how a 1 % tweak in μ affects the long‑term evolution—no need for fancy math, just a few dozen steps and you’ll see the orbits wobble in and out of the chaotic zone. Let me know if you want to dive into that.
NotEasy NotEasy
Sounds good—let's tweak μ by 1 % and see if the “traffic jam” clears or gets denser. I'll set up a quick N‑body run with a dozen steps and watch the orbits jitter. Give me the initial conditions and I'll run the numbers.