カイパーベルトの構造:太陽系外縁に存在する惑星の証拠

抄録

Trans-Neptunian objects (TNOs) orbit in the so called trans-Neptunian belt (or Edgeworth-Kuiper belt). These icy bodies represent the relics of planet accretion in the outer solar system. We investigated the structure of the trans-Neptunian belt by conducting extensive computer simulations (4-5Gyr) using tens of thousands of particles in planetesimal disks. After taking into account several observational constraints, we developed a model to explain the origin and evolution of the belt by considering a hypothetical outer planet (or planetoid) with tenths of Earth masses orbiting beyond about 100AU.An outer planet in a distant orbit in the scattered disk can explain the ancient trans-Neptunian belt excitation, the formation of an outer edge at ~48AU, the entire TNO resonant population, the formation of detached TNOs and many other features in a self-consistent way. Noteworthy, the results match very well up-to-date observations. The best constraints obtained from the model for the planetoid are: aP=100-170AU, qP>80AU, iP=30-50 degrees, albedo=0.1-0.3, and apparent magnitude mP=15~17mag at perihelion.In summary, our model with the existence of a distant massive planet successfully describes the trans-Neptunian belt architecture with an unprecedented level of details.