## Kirkwood gaps in asteroid orbits

Fig. 12.3 . Most of the asteroids are found in the asteroid belt that lies between 2.2 and 3.3 AU from the Sun, but here are very few asteroids at certain distances from the Sun. These Kirkwood gaps have orbital periods of 1/4, 1/3, 2/5, 3/7 and 1/2 of Jupiter’s orbital period. These fractions are placed above the relevant gap in the figure. The fraction 1/4 indicates, for example, that an asteroid at that distance makes 4 revolutions around the Sun for each 1 revolution completed by Jupiter. Asteroids are tossed out of such resonant orbits by Jupiter’s repeated gravitational perturbations. In addition, there are several peaks corresponding to groups of asteroids with nearly the same orbital distance, such as the Trojan asteroids that have orbits that are identical in size to the orbit of Jupiter.

Copyright 2010, Professor Kenneth R. Lang, Tufts University