Five-planet Nice model
A revised model of early Solar System evolution with five giant planets.
The five-planet Nice model is a numerical model of the early Solar System, first formally proposed in 2011, that revises the original Nice model by beginning with five giant planets—the four that exist today plus an additional ice giant between Saturn and Uranus in a chain of mean-motion resonances. After the resonance chain breaks, the planets undergo planetesimal-driven migration and a period of orbital instability, during which the extra ice giant is ejected from the Solar System following an encounter with Jupiter. The model was developed because simulations indicated it was more likely to reproduce the current Solar System than a four-planet Nice model.
- field
- Planetary science / Solar System dynamics
- known_for
- Proposing an early Solar System with five giant planets, one of which was ejected
- first_formally_proposed
- 2011
- key_feature
- Additional ice giant between Saturn and Uranus in a resonance chain
Lore & Background
The five-planet Nice model begins with Jupiter, Saturn, and three ice giants in a 3:2, 3:2, 2:1, 3:2 resonance chain, with semi-major axes ranging from 5.5 to 20 AU. A dense disk of planetesimals orbits beyond these planets, extending from 24 AU to 30 AU. Gravitational interactions among planetesimals stir their orbits, causing the disk to spread and push its inner edge toward the giant planets. Collisions produce dust that spirals inward via Poynting-Robertson drag, and interactions with this dust or inward-scattered planetesimals allow the planets to escape the resonance chain roughly ten million years after the gas disk dissipates.
Reader's Guide
The five-planet Nice model is significant because it offers a more statistically likely explanation for the current configuration of the Solar System than the original four-planet Nice model. It accounts for the ejection of an extra ice giant, which explains the absence of a fifth giant planet today. The model also reproduces many observed features of the outer Solar System, including the formation of the hot classical Kuiper belt, the scattered disk, the cold classical Kuiper belt with its low-inclination, low-eccentricity objects near 44 AU, and the capture of Jupiter trojans and irregular satellites. In the inner Solar System, an early instability could explain the small size of Mars and the depletion and excitation of the asteroid belt. The model preserves uncertainty about the timing of the giant planet instability, noting that some studies link it to the Late Heavy Bombardment while others indicate it occurred early.
Did You Know?
- The five-planet Nice model was first formally proposed in 2011 after simulations indicated it was more likely to reproduce the current Solar System than a four-planet model.
- During the instability, the extra ice giant is scattered inward onto a Jupiter-crossing orbit and ejected from the Solar System following an encounter with Jupiter, becoming a rogue planet.
- The model can produce a group of low-inclination, low-eccentricity objects in the cold classical Kuiper belt with semi-major axes near 44 AU when Neptune's 2:1 resonance releases captured planetesimals.
- An early instability from this model could have removed most mass from the Mars region, leaving Mars smaller than Earth and Venus.
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