Severe instability marked the early stages of Sistema Solar’s formation. Planetas giants changed positions about 4 billion years ago. Esse rearrangement generated dangerous approaches between them. The regular Júpiter and Urano satellites were at real risk of destruction during the process.
Pesquisadores Americans simulated thousands of scenarios to understand how the moons survived. The results show that the presence of an extra planet, later removed, was decisive. Sem it, the circular and aligned orbits of large satellites would hardly have been maintained.
Aproximações among giants threatened moon systems
Giant planets formed closer together than they are today. Durante instability, they passed distances of less than 15 million kilometers in many cases. Essa proximity generated gravitational forces that perturbed the orbits of nearby satellites.
Júpiter’s four main satellites — Io, Europa, Ganimedes and Calisto — orbit between 400,000 and 2 million kilometers from the planet. A strong external disturbance could lengthen these trajectories. The result would be collisions, falls into the atmosphere or expulsions into interstellar space.
Situação was similar for the regular moons of Urano. Suas orbits are also circular and equatorial. Qualquer severe imbalance would compromise the current configuration.
Simulações tested 122 planetary migration scenarios
The team led by Matthew Clement, from Universidade Johns Hopkins, selected 122 trajectories that reproduce the current position of the planets. It then ran 1,464 detailed simulations of the satellites’ behavior under gravitational influence.
The Frontera supercomputer, at Texas, processed each case for two to three months. The calculations included interactions with Sol and the other bodies.
- Probabilidade survivability of Júpiter’s moons was below 15% in most scenarios
- Similar Chance, less than 15%, to the moons of Urano
- Probabilidade joint survivability of the two systems dropped to around 1%
Distâncias criticisms have been identified. Aproximações of Urano less than 3 million kilometers from another ice giant led to total destruction. Contatos with Júpiter or Saturno below 15 million kilometers also resulted in a complete loss.
Cenário with six planets showed greater stability
Apenas two complete scenarios allowed the simultaneous survival of the moons of Júpiter and Urano. Ambos included a fifth ice giant, with a mass between six and eight times that of Terra.
Essa additional planet changed the migration dynamics. Ela prevented Urano from getting too close to other bodies at critical moments. Júpiter, in turn, ended up ejecting the intruder out of Sistema Solar with a strong gravitational push.
The lost planet probably wanders today in interstellar space. Sua output wasn’t what saved the moons directly. His presence before the ejection stabilized the movements enough for the regular orbits to hold.
Como the current moons of Urano formed
The simulations also helped explain the configuration of the Uranian moons. The impact that tilted Urano’s axis occurred during a compatible period. The temporary presence of the fifth giant reduced the number of subsequent destructive collisions.
Regular satellites remained in stable orbits after the initial chaos. Isso reinforces the idea that the current Sistema Solar is the result of a delicate balance, influenced by a member that no longer exists.
Implicações for planetary formation models
The findings reinforce the validity of the call Modelo of Nice, which describes the migration of the giants. Eles also indicate that systems with five or six initial giant planets best fit the observed data.
Future Pesquisas may look for indirect evidence of the ejected planet. Trans-Neptunian Objetos with peculiar orbits or anomalies in the Kuiper belt are potential targets.
The team published the results in a revised scientific article. Detailed calculations are available in an open repository for verification by other groups.