Gap or dip in the distribution of the semi-major axes of the orbits of main-belt asteroids
Histogram showing the four most prominent Kirkwood gaps and a possible division into inner, middle and outer main-belt asteroids: inner main-belt (a < 2.5 AU) intermediate main-belt (2.5 AU < a < 2.82 AU) outer main-belt (a > 2.82 AU)A plot of inner solar system asteroids and planets as of 2006 May 9, in a manner that exposes the Kirkwood gaps. Similar to the position plot, planets (with trajectories) are orange, Jupiter being the outer most in this view. Various asteroid classes are colour coded: 'generic' main-belt asteroids are white. Inside the main belt, there are the Atens (red), Apollos (green), and Amors (blue). Outside the main belt are the Hildas (blue) and the Trojans (green). All object position vectors have been normalized to the length of the object's semi-major axis. The Kirkwood gaps are visible in the main belt.
A Kirkwood gap is a gap or dip in the distribution of the semi-major axes (or equivalently of the orbital periods) of the orbits of main-belt asteroids. They correspond to the locations of orbital resonances with Jupiter.
For example, there are very few asteroids with semimajor axis near 2.50 AU, period 3.95 years, which would make three orbits for each orbit of Jupiter (hence, called the 3:1 orbital resonance). Other orbital resonances correspond to orbital periods whose lengths are simple fractions of Jupiter's. The weaker resonances lead only to a depletion of asteroids, while spikes in the histogram are often due to the presence of a prominent asteroid family (see List of asteroid families).
The gaps were first noticed in 1866 by Daniel Kirkwood, who also correctly explained their origin in the orbital resonances with Jupiter while a professor at Jefferson College in Canonsburg, Pennsylvania.[1]
Most of the Kirkwood gaps are depleted, unlike the mean-motion resonances (MMR) of Neptune or Jupiter's 3:2 resonance, that retain objects captured during the giant planet migration of the Nice model. The loss of objects from the Kirkwood gaps is due to the overlapping of the ν5 and ν6 secular resonances within the mean-motion resonances. The orbital elements of the asteroids vary chaotically as a result and evolve onto planet-crossing orbits within a few million years.[2] The 2:1 MMR has a few relatively stable islands within the resonance, however. These islands are depleted due to slow diffusion onto less stable orbits. This process, which has been linked to Jupiter and Saturn being near a 5:2 resonance, may have been more rapid when Jupiter's and Saturn's orbits were closer together.[3]
More recently, a relatively small number of asteroids have been found to possess high eccentricity orbits which do lie within the Kirkwood gaps. Examples include the Alinda and Griqua groups. These orbits slowly increase their eccentricity on a timescale of tens of millions of years, and will eventually break out of the resonance due to close encounters with a major planet. This is why asteroids are rarely found in the Kirkwood gaps.
^Cite error: The named reference Coleman-1956 was invoked but never defined (see the help page).
^Cite error: The named reference Moon-1995 was invoked but never defined (see the help page).
^Cite error: The named reference Moons-1998 was invoked but never defined (see the help page).
A Kirkwoodgap is a gap or dip in the distribution of the semi-major axes (or equivalently of the orbital periods) of the orbits of main-belt asteroids...
forms an orbital resonance with Jupiter. At these orbital distances, a Kirkwoodgap occurs as they are swept into other orbits. In 1596, Johannes Kepler...
Kirkwood may refer to: Kirkwood Islands, string of islands near Antarctica Kirkwood Range, massive coastal mountain chain in Antarctica Mount Kirkwood...
to observe, or removed from the asteroid belt by approaching the 3:1 Kirkwoodgap, by the Yarkovsky effect, or (in the case of small fragments) by radiation...
several gaps, now named Kirkwoodgaps in his honor, and associated these gaps with orbital resonances with the orbit of Jupiter. Further, Kirkwood also suggested...
resonance with Jupiter of 9:2, and with Mars of 2:3 The 4:1 resonance Kirkwoodgap (at 2.06 AU) marks the outer boundary of the Hungaria family, while interactions...
evidence of the existence of an exomoon with mass up to 0.8 Earth masses. Kirkwoodgap Subsatellite (a moon of a moon) Goldreich, Peter; Tremaine, Scott (1979)...
Earth years, specifically in the inner asteroid belt, interior to the Kirkwoodgap at 2.50 AU. Its orbit is moderately inclined (i = 7.1°, compared to 7°...
asteroids. Some of the more far-flung asteroid debris ended up in the 3:1 Kirkwoodgap. This is an unstable region due to strong perturbations by Jupiter, and...
0.067. The semimajor axis of 2.47 AU is slightly inward from the 3:1 KirkwoodGap. Its orbital plane is inclined by 4° to the plane of the ecliptic. On...
planets of intermediate size are typical—both rocky and gas—so there is no "gap" as seen between the size of Earth and of Neptune (with a radius 3.8 times...
the Hungaria asteroids, which orbit the Sun on the inside of the 1:4 Kirkwoodgap, standing out of the core of the asteroid belt. It was discovered by...
C-type asteroids that are dominant in the outer asteroid belt, beyond the Kirkwoodgap at 2.82 AU. Its mean diameter 433±8 km. Hygiea is close to spherical...
demonstrated for the first time the theoretical reason for the clearing of the Kirkwoodgaps in the asteroid belt. His work has also brought to light the chaotic...
astronomer Daniel Kirkwood (1814–1895), long-time professor of mathematics at Indiana University. He discovered the Kirkwoodgaps, which are gaps in the distribution...
located in the inner parts of the intermediate asteroid belt, near the 1:3 Kirkwoodgap. The family consist of several thousand stony S-type asteroids. It is...
closer to Jupiter's orbital plane than the Sun's equatorial plane. The Kirkwoodgaps in the asteroid belt are mostly caused by Jupiter, and the planet may...
University who discovered the divisions of the asteroid belt known as the KirkwoodGaps. Built in 1900 and dedicated on May 15, 1901, the observatory was thoroughly...
The inner asteroid belt (defined as the region interior to the 3:1 Kirkwoodgap at 2.50 AU) has few large asteroids. Of those in the above list, only...
714 Ulula is a main belt asteroid. It is orbiting the Sun near the 3:1 KirkwoodGap with a period of 4.04 years and an eccentricity of 0.057. It was discovered...
rule observed a gap between Mars and Jupiter void of any known planet. In 1801 Giuseppe Piazzi discovered Ceres, a body that filled the gap and was regarded...
parent body. 695 Bella and 6 Hebe orbit on opposite sides of the 3:1 Kirkwoodgap, and the two have similar orbital elements. "695 Bella (1909 JB)". JPL...
a dynamic member of the Maria asteroid family orbiting near the 3:1 Kirkwoodgap. This is an S-type (stony) asteroid spanning 27 km. The surface mineralogy...
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