Patryk Sofia Lykawka

Dynamical models for the inner and outer solar system: Forming the terrestrial planets, the asteroid belt, and the orbital structure in the distant Kuiper Belt

The solar system possesses properties that are challenging to explain. In particular, simultaneously replicating the four terrestrial planets’ orbits/masses and the asteroid belt’s main properties remain elusive. Also, the orbital structure of TNOs in the distant Kuiper Belt beyond ~50 au is unlikely to result from the perturbations of the currently known giant planets. Our approach to this study was thorough and comprehensive. We used N-body computer simulations to investigate the simultaneous formation of the four terrestrial planets and the asteroid belt within the Jupiter–Saturn chaotic excitation (JSCE) scenario. We also explored the effects of a hypothetical Kuiper Belt planet (KBP) on the distant Kuiper Belt, leaving no stone unturned in our quest for understanding this poorly explored region. An analysis of 37 optimally formed terrestrial planet systems allowed us to constrain the planets’ building blocks, accretion history, and other fundamental properties. Our terrestrial planets closely resembled those in our solar system, including their orbits, masses, and accretion history. The model asteroid belt also accurately represented its orbital structure, small mass, and asteroid types. Other key results include Moon-forming giant impacts occurring within ~60 Myr, the bulk water acquired during the first 10–20 Myr of Earth’s formation, and the asteroid belt being a mixture of local survivors and captured asteroids. Our study has also led to some intriguing predictions. We have determined that an Earth-mass planet (m ~ 1.5–3 M⊕) located on a distant (semimajor axis a ~ 250–500 au, perihelion q ~ 200 au) and inclined (i ~ 30 deg) orbit can explain three fundamental properties of the distant Kuiper Belt. These properties include a prominent population of TNOs with orbits beyond Neptune’s gravitational influence (i.e., detached objects with q > 40 au), a significant population of high-i objects (i > 45 deg), and the existence of some extreme objects with peculiar orbits (e.g., Sedna). We predict the existence of an Earth-mass planet and several TNOs on peculiar orbits in the outer solar system. These predictions can serve as observationally testable signatures of the putative planet’s perturbations, opening up exciting avenues for future research.