Kirkwood gap

A region of reduced asteroid density at a particular orbital distance in the asteroid belt. These gaps arise mainly from orbital resonances with Jupiter that destabilize asteroid orbits.

Orbital resonance: A relationship in which orbiting bodies’ periods form a ratio of small whole numbers. Resonances with Jupiter repeatedly perturb asteroids in the gaps.
Asteroid belt: A region of the Solar System between Mars and Jupiter containing many small rocky bodies. Kirkwood gaps are depleted zones within this population.
2:1 mean-motion resonance: A mean-motion resonance in which one body completes one orbit while another completes two. This resonance produces a prominent Kirkwood gap near 3.28 astronomical units.
Daniel Kirkwood: An American astronomer who identified regular gaps in the distribution of asteroid orbital periods. The gaps bear his name after his nineteenth-century analysis of asteroid orbits.
Mean-motion resonance: An orbital resonance in which two bodies’ average orbital periods form a ratio of small whole numbers. Kirkwood gaps align with specific mean-motion resonances between asteroids and Jupiter.
Asteroid: A small rocky or metallic body orbiting the Sun, smaller than a dwarf planet. The gaps describe the distribution of asteroids by orbital distance.
3:1 mean-motion resonance: A mean-motion resonance in which one body completes one orbit while another completes three. The strong gap near 2.50 astronomical units is associated with this resonance with Jupiter.
Asteroid discovery: The observation and identification of small Solar System bodies orbiting the Sun. Growing asteroid catalogs made patterns in orbital distributions visible.
Jupiter: The largest planet in the Solar System, orbiting beyond the asteroid belt. Its gravity drives the resonances that clear many Kirkwood gaps.
Orbital period: The time a body takes to complete one orbit around another body. Period ratios with Jupiter identify the resonances associated with gaps.

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