Kirkwood gaps

(kerk -wûd) Gaps in the distribution of orbits within the main asteroid belt, corresponding to the absence of orbits with periods that are simple fractions (1/4, 1/3, 2/5, 1/2, etc.) of the orbital period of Jupiter (see illustration). Asteroids with such orbital periods would be perturbed into orbits of high eccentricity by the regularly recurring gravitational pull of Jupiter. These asteroids would then cross the orbits of Mars and Earth, with a high chance of colliding with these planets. The US astronomer Daniel Kirkwood first explained these gaps in 1857.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

Kirkwood gaps

[′kərk‚wu̇d ‚gaps]

(astronomy)

Regions in the main zone of asteroids where almost no asteroids are found.

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References in periodicals archive

Daniel Kirkwood born; an American astronomer; studied the orbits of the asteroids; discovered the Kirkwood Gaps in the asteroid belt; wrote on comets, meteorites and asteroids.

Centenaries for 2014

Called Kirkwood gaps, they are thought to be cleared of debris by Jupiter's gravity, which causes any objects orbiting there to move chaotically.

Jupiter and Saturn's migratory ways may have shaped asteroid belt

Once astronomers understood the Kirkwood gaps, a clearer picture of the origin of the asteroid belt emerged.

As discoveries increased, almost every small number ratio of Jupiter's orbital period (such as 1:2, 1:3, 2:5, and 3:7) seemed to have a Kirkwood gap associated with it, while a few (such as 2:3 and 1:1) yielded concentrations.

His computer simulations revealed that a hypothetical asteroid placed in a circular orbit 2.5 astronomical units from the Sun (corresponding to the 1:3 Kirkwood gap) undergoes a very large--but not precisely predictable--increase in its orbital eccentricity after only 100,000 years or so.

A new century for asteroids

Likely places where such activity might occur include the Kirkwood gaps, regions in the main belt where the supply of asteroids is much lower than in other areas.

The Kirkwood gaps have a unique feature: The orbital motion of any asteroid at one of these locations has a special relationship, called a resonance, with Jupiter.

Rocky relics: getting the lowdown on near-Earth asteroids

It was clear that they were not evenly distributed, and the American astronomer Daniel Kirkwood (1814-1895) showed in 1866 that there were definite gaps, since called "Kirkwood gaps."

Kirkwood gaps

Interestingly it lies quite close to one of the Kirkwood Gaps having a 5:2 resonance with the planet Jupiter.

Asteroid (229255) Andrewelliott

Breaks in the belt, known as Kirkwood gaps, are relatively empty rings, swept free of asteroids.

Clean Sweep: The galaxy is so untidy. There are gas, dust, and asteroids strewn everywhere