Kirkwood gap
A Kirkwood gap is a gap or dip in the distribution of the
For example, there are very few asteroids with semimajor axis near 2.50
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
More recently, a relatively small number of asteroids have been found to possess high
Main gaps
The most prominent Kirkwood gaps are located at mean orbital radii of:[4]
- 1.780 AU (5:1 resonance)
- 2.065 AU (4:1 resonance)
- 2.502 AU (3:1 resonance), home to the Alinda groupof asteroids
- 2.825 AU (5:2 resonance)
- 2.958 AU (7:3 resonance)
- 3.279 AU (2:1 resonance), Hecuba gap, home to the Griqua groupof asteroids.
- 3.972 AU (3:2 resonance), home to the Hilda asteroids.
- 4.296 AU (4:3 resonance), home to the Thule group of asteroids.
Weaker and/or narrower gaps are also found at:
- 1.909 AU (9:2 resonance)
- 2.258 AU (7:2 resonance)
- 2.332 AU (10:3 resonance)
- 2.706 AU (8:3 resonance)
- 3.031 AU (9:4 resonance)
- 3.077 AU (11:5 resonance)
- 3.474 AU (11:6 resonance)
- 3.517 AU (9:5 resonance)
- 3.584 AU (7:4 resonance), home to the Cybele asteroids
- 3.702 AU (5:3 resonance).
Asteroid zones
The gaps are not seen in a simple snapshot of the locations of the asteroids at any one time because asteroid orbits are elliptical, and many asteroids still cross through the radii corresponding to the gaps. The actual spatial density of asteroids in these gaps does not differ significantly from the neighboring regions.[5]
The main gaps occur at the 3:1, 5:2, 7:3, and 2:1 mean-motion resonances with Jupiter. An asteroid in the 3:1 Kirkwood gap would orbit the Sun three times for each Jovian orbit, for instance. Weaker resonances occur at other semi-major axis values, with fewer asteroids found than nearby. (For example, an 8:3 resonance for asteroids with a semi-major axis of 2.71 AU).[6]
The main or core population of the asteroid belt may be divided into the inner and outer zones, separated by the 3:1 Kirkwood gap at 2.5 AU, and the outer zone may be further divided into middle and outer zones by the 5:2 gap at 2.82 AU:[7]
- 4:1 resonance (2.06 AU)
- Zone I population (inner zone)
- 3:1 resonance (2.5 AU)
- Zone II population (middle zone)
- 5:2 resonance gap (2.82 AU)
- Zone III population (outer zone)
- 2:1 resonance gap (3.28 AU)
See also
- Orbital resonance
- Alinda group
- Cybele group
- Griqua group
References
- OCLC 2191890.
- .
- .
- S2CID 2049956. Retrieved 13 December 2016.
- Bibcode:1990MNRAS.244..513M.
- Bibcode:1994IAUS..160..175F.
- S2CID 123074137.
External links
- Article on Kirkwood gaps at Wolfram's scienceworld