Nice model

The Nice model, according to the city of Nice is one in 2005 by Gomes, Levison, Morbidelli and Tsiganis proposed ( in alphabetical order) in three Nature articles model for a late migration of the planets in the solar system. It is able to predict some properties of the solar system.

The model

The model describes a migration of the planet, after the protoplanetary gas disk has dissipated, so it is not a migration model in the strict sense. The model assumes that the planetary originally ran on nearly circular orbits compact web. Furthermore, the model assumes that planet formation a disk of planetesimals was that to also ranged from outside the planet orbits at a distance of 35 AU and had a total mass of about 35 Earth masses.

The giant planets of the solar system now scatter planetesimals initially isolated from the disk, while angular momentum is transferred and the path of the planets change slightly. It can be shown by numerical simulations that this Saturn, Uranus and Neptune slowly slowly migrate outwards and Jupiter inward.

After a few hundred million years, there is a 2:1 resonance ( english mean motion resonance, MMR ) between Jupiter and Saturn. This increases the eccentricities and the system destabilizes. The planet Saturn Uranus and Neptune come close to each other and the disk of planetesimals. Thus, the planetesimals are scattered practically abruptly, part of the planetesimals flies into the inner solar system and triggers the Great from bombing.

After about a hundred million years, the planet eventually reach its present distance, their Exzentizitäten are damped and the system stabilizes again.

In addition to the positions, eccentricities and inclinations of the giant planets and the Great bombardment, the model explains a number of other characteristics of today's solar system:

• While the global instability, the co -orbit of Jupiter regions are gravitationally open. The scattered Planetisimale can fly at this time in any of these regions in and out. At the end of the phase instability regions are comparatively suddenly closed gravitationally again and the objects that were at this time there are trapped. This explains the Jupiter Trojan and Hilda asteroids. The same also applies for the Trojans of Neptune. The model agrees in all essential characteristics of the Trojans - until their large inclinations - match.
• Saturn, Uranus and Neptune came and the Planetisimalen close during the global instability, therefore, triple collisions between two planets and planetesimal are comparatively likely. In such encounters the planetesimal is captured by one of the two planets and orbits this from now on as the moon. Since there is no requirement that the moon should orbit the planet in the equatorial plane, you get a at the outer planets frequently occurring irregular moon. This can be explained by the irregular moons of Jupiter principle of the giant planets. The predictions agree with respect to inclination, eccentricity and semi-major axis consistent with the observations. The first predicted mass distribution of the planet does not correspond to the measured, this can be explained, however, if one assumes that there has been a collision between the irregular moons.
• 99 % of the mass of the planetesimal disc goes through the shock lost - the remaining body, however, form the Kuiper belt. In this case, the model is able to explain all the important properties of the Kuiper belt, which before that, no model is also successful: The co- existence of resonant and non-resonant objects
• The relative distribution of semi-major axis and eccentricity of the Kuiper Belt
• The existence of an outer edge at the distance of a 2:1 resonance with Neptune
• The bimodal distribution of the objects and while existing correlation between the inclination and the characteristics of the object
• The orbital distribution of the Plutinos and the 2:5 - calibrators ( one in 1975 described by Franklin et al. class of asteroids )
• The existence of the extended scattered disc
• The mass deficit of the Kuiper Belt

Critique and extension

The model does not describe the migration in the protoplanetary gas disk, but it is only at it. The problems and open questions in classical planetary migration are thus not resolved.

In developing the model, only the four giant outer planets were considered, the effect on the orbits of the terrestrial planets were not considered. In the instability phase, this would most likely not be disturbed. Even so unstable systems tend to lose the planet. Both can possibly be avoided by allowing the system initially adds another giant planets, which is the system stabilizes and finally threw himself out of the solar system. David Nesvorny of the Southwest Research Institute showed in 2011 that the probability is much higher than for a model without a fifth giant planet. Here, a variety of simulations with different initial conditions, migration rates of planets, dissolution rates of the gas disk, the disk of planetesimals masses and masses of additional planets (between 1 /3 and 3 Uranus mass ) were made and evaluated according to four criteria:

• Criterion A: At the end of the system must have exactly four giant planets.
• Criterion B: The planet must end up with similar orbits to observable today. ( eg max 20% deviation in the Great semi-axis ).
• Criterion C: Certain parameters must be such that the possibility of capture of irregular moons - as described above - is.
• Criterion D: The distance between Jupiter and Saturn must be such that the inner terrestrial planets survive.

In the analysis it was found that the criterion is satisfied A at the beginning of 4 giant planets in less than 13 % of the simulations, while it is true at the beginning 5 planets in 37% of the simulations; Criterion B is at 4 planets in only 2.5% of cases met while it is satisfied upon addition of a 5 planets in 23 % of cases. With proper selection of the mass of the fifth planet from 1/2 Uranus mass probabilities for criterion A and B even rise to 50 % and 20-30%. The inner planets survive in the classical model in only about 1% of cases - when a planet to the extended model, however, the probability rises to about 10%.

However, the study also shows that the criterion C is in both models only very rarely met, since the model can not describe the irregular moons of Jupiter, it is questionable whether it can be used to explain irregular moons.