- Gaps in the asteroid belt where few if any asteroids are found. The gaps are caused by resonances with the orbital period of Jupiter. Asteroids in the gaps would have periods of a third, two fifths, three sevenths, a half or three fifths of one Jovian year, subjecting them to severe gravitational disturbance by Jupiter at regular intervals. This means that the gaps are swept clear of asteroids. The same resonance effects are responsible for sweeping clear the gaps in planetary rings, which are also sometimes called Kirkwood Gaps. US astronomer Daniel Kirkwood (1814–1895) investigated both types of solar system resonance in the 1860s.