Nice model

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A simulation based on the Nice model showing the outer planets and the Kuiper belt :
a) before the Jupiter / Saturn 2: 1 resonance, b) dispersion of the objects of the Kuiper belt into the solar system after the orbit of Neptune had shifted, c) after the ejection of objects of the Kuiper Belt by Jupiter

The Nice model ( English Nice model , pronunciation : [ ˈniːs ], after the city of Nice , where it was developed at the Observatoire de la Côte d'Azur ) is a model for a late migration of the planets in the solar system , which was published in 2005 by R. Gomes, HF Levison, A. Morbidelli, and K. Tsiganis (in alphabetical order) in three Nature articles. The model can predict a number of properties of the solar system.

The model

Position of the giant planets as a function of time. You can see the instability phase, triggered by the 2: 1 MMR (dashed line), and the exchange of Uranus and Neptune.

The model describes a migration of the planets after the protoplanetary gas disk has dissolved. So it is not a migration model in the strict sense of the word, such as the grand tack model . The Nice model assumes that the planets originally ran in nearly circular, compact orbits . It also assumes that the formation of planets produced a disk of planetesimals that extended from outside the planetary orbit up to a distance of 35  AU and had a total mass of about 35  Earth's masses .

The giant planets of the solar system are now initially scattering planetesimals from the disk. Here, angular momentum transfer and the orbits of the planets are changing slightly. With numerical simulations it can be shown that Saturn , Uranus and Neptune slowly move outwards and Jupiter inwards.

After a few hundred million years (500–800 million years after the sun was formed) there is a 2: 1 resonance ( English mean motion resonance , MMR ) between Jupiter and Saturn. This increases the eccentricities and destabilizes the system. The planets Saturn, Uranus and Neptune come close to each other and to the disk of planetesimals. As a result, the planetesimals are practically suddenly scattered, part of the planetesimals flies into the inner planetary system and triggers the great bombardment there. In around 50 percent of the simulated models, there is also a change of location between the two outermost gas planets Uranus and Neptune (see the graphic on the right). After about a hundred million years, the planets finally reach their present distances, their eccentricities are dampened and the system stabilizes again.

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

  • During global instability, Jupiter's co-orbit regions are gravitationally open. The scattered planetesimals can fly in and out of these regions at will during this time. At the end of the instability phase, the regions are relatively suddenly closed again gravitationally, and the objects that were there at this point in time are trapped. This explains the Jupiter Trojans and Hilda asteroids . The same applies to the Neptune Trojans. The model agrees in all essential properties of the Trojans - except for their large inclinations.
  • Saturn, Uranus and Neptune came close to each other and the planetesimals during global instability, so triple collisions between two planets and a planetesimal are relatively likely. In such encounters, the planetesimal is captured by one of the two planets and from then on orbits it as the moon . Since there is no need for the moon to orbit the planet in the equatorial plane , an irregular moon is obtained, which is common in the outer planets . This can in principle explain the irregular moons of the giant planets except for those of Jupiter. The predictions agree with the observations regarding inclination, eccentricity and semi-major axis . The initially predicted mass distribution of the planets does not correspond to the measured one; however, this can be explained if one assumes that there have been collisions between the irregular moons.
  • 99% of the mass of the planetesimal disk is lost through the impact - the remaining bodies, however, form the Kuiper belt . The model is able to explain all the important properties of the Kuiper belt, something that no model has succeeded in doing at the same time:
    • the coexistence of resonant and non-resonant objects
    • the relative distribution of the semi-major axis and the eccentricity of the Kuiper belt
    • the existence of an outside edge at the distance of a 2: 1 resonance with Neptune
    • the bimodal distribution of the objects and the correlation between the inclination and the properties of the object
    • the orbital distribution of the plutinos and the 2: 5 librators (a class of asteroids described by Franklin et al. in 1975 )
    • the existence of the extended scattered disc
    • the mass deficit of the Kuiper Belt.

Criticism and expansion

As in the figure above, you can see the destabilization after the 2: 1 MMR and how Neptune jumps over Uranus. However, the hypothetical fifth planet is taken into account here, you can see how it is thrown out of the system during the instability phase.

The model does not describe the migration in the protoplanetary gas disk, but starts afterwards. The problems and open questions of classic planetary migration are therefore not solved.

When developing the model, only the four outer giant planets were considered; the effects on the orbits of the terrestrial planets were not taken into account. In the instability phase, however, these would likely be disturbed . Such unstable systems also tend to lose planets. Both of these can possibly be avoided by initially adding another giant planet to the system, which stabilizes the system and is eventually thrown out of the solar system itself.

David Nesvorny of the Southwest Research Institute showed in 2011 that this is much more likely than a model without a fifth giant planet. A large number of simulations with different initial conditions , migration rates of the planets, dissolution speeds of the gas disk, masses of the disk from planetesimals and masses of the additional planet (between 1/3 and 3 Uranus masses) were made and evaluated according to four criteria:

  • Criterion A: In the end, the system must have exactly 4 giant planets.
  • Criterion B: In the end, the planets must have orbits comparable to those that can be observed today. (e.g. max. 20% deviation in the major semi-axis).
  • Criterion C: Certain parameters must be such that there is the possibility of catching irregular moons - as described above.
  • Criterion D: The distance between Jupiter and Saturn must be such that the inner terrestrial planets survive.

During the evaluation, it was found that criterion A is met in under 13% of the simulations with initially 4 giant planets, while it is met in 37% of the simulations with 5 planets initially; Criterion B is fulfilled in only 2.5% of the cases with 4 planets, while it is fulfilled in 23% of the cases with the addition of a 5th planet. With the correct choice of the mass of the fifth planet of 1/2 mass of Uranus, the probabilities for criterion A and B even increase to 50% and 20–30%, respectively. In the classical model, the inner planets only survive in about 1% of the cases - in the model expanded by one planet, the probability increases to about 10%.

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

literature

  • K. Tsiganis, R. Gomes, A. Morbidelli, HF Levison: Origin of the orbital architecture of the giant planets of the Solar System . In: Nature . tape 435 , no. 7041 , May 26, 2005, p. 459–461 , doi : 10.1038 / nature03539 ( PDF ).
  • A. Morbidelli, HF Levison, K. Tsiganis, R. Gomes: Chaotic capture of Jupiter's Trojan asteroids in the early Solar System . In: Nature . tape 435 , no. 7041 , May 26, 2005, p. 462-465 , doi : 10.1038 / nature03540 ( PDF ).
  • R. Gomes, HF Levison, K. Tsiganis, A. Morbidelli: Origin of the cataclysmic Late Heavy Bombardment period of the terrestrial planets . In: Nature . tape 435 , no. 7041 , May 26, 2005, p. 466–469 , doi : 10.1038 / nature03676 ( PDF ).
  • Aurélien Crida: Solar System formation . In: Earth and Planetary Astrophysics (astro-ph.EP) . March 17, 2009, arxiv : 0903.3008v1 .
  • David Nesvorny: Young Solar System's Fifth Giant Planet? In: Earth and Planetary Astrophysics (astro-ph.EP) . September 13, 2011, arxiv : 1109.2949 .

Web links

Individual evidence

  1. ↑ K. Tsiganis, R. Gomes, A. Morbidelli, HF Levison: Origin of the orbital architecture of the giant planets of the Solar System . In: Nature . tape 435 , no. 7041 , May 26, 2005, ISSN  0028-0836 , p. 459-461 , doi : 10.1038 / nature03539 ( nature.com ).
  2. ↑ Franklin et al., Minor planets and comets in libration about the 2: 1 resonance with Jupiter