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Mean-Motion Resonance and Kirkwood Gaps

What you are seeing: the asteroid belt (orange dots) has gaps where Jupiter's 2:1, 3:1, 5:2 etc. mean-motion resonances pump up asteroid eccentricities until they leave the belt. The dashed lines mark the resonance semi-major axes.

Figure 1. Kirkwood-gap map and resonance locations.
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WHAT TO TRY

  • Watch the Kirkwood gaps open at the 2:1, 3:1 and 5:2 commensurabilities: asteroids parked there get repeated kicks from Jupiter that pump their eccentricity until they leave. The dashed lines mark the resonant radii.
  • Change the belt population and let it run: the gaps clear over time as resonant bodies are removed, while between-resonance orbits stay put. The gaps are sculpted, not primordial.
  • Speed up the integration to see the long-term sculpting: the resonance is a slow eccentricity pump, so depletion only shows over many orbits.