The structure, dynamics, and origin of the solar system fall within the domains of planetary science, observational astronomy, and astrophysics. Within these communities, broad consensus exists on the heliocentric model, the approximate age and formation of the solar system, planetary classification, and the general mechanics governing orbital motion. Partial consensus exists on several questions of solar system formation and early dynamics. Active debate continues on the precise mechanisms of planetary migration, the classification boundaries of small bodies, and the existence and location of hypothetical outer planets.
Within planetary science and observational astronomy, consensus is complete that the Sun occupies the gravitational center of the solar system and that the planets orbit it. This position is supported by centuries of direct observation, spacecraft telemetry, radar ranging, and the predictive success of Newtonian and Einsteinian gravitational models. No professional astronomical body disputes heliocentrism as a description of solar system structure. For historical development of this consensus, see Heliocentrism - History.
Radiometric dating of meteorites - particularly calcium-aluminum-rich inclusions (CAIs) in carbonaceous chondrites - places the age of the solar system at approximately 4.568 billion years, with an uncertainty of a few million years.1) This figure is consistent across multiple independent radiometric systems (uranium-lead, samarium-neodymium, hafnium-tungsten) and is accepted across planetary science, geochemistry, and cosmochemistry.
The nebular hypothesis - that the solar system formed from the gravitational collapse of a rotating disk of gas and dust - is the consensus formation model. Observational support comes from protoplanetary disks observed around young stars, isotopic anomalies in primitive meteorites, and the coplanar, prograde orbital structure of the major planets.2)
Kepler's laws of planetary motion and Newtonian gravitational mechanics accurately predict planetary orbits to high precision. Relativistic corrections (general relativity) are required for high-precision work, particularly for Mercury's perihelion precession, and are incorporated into standard models. These frameworks are validated by spacecraft navigation across the solar system and are not in dispute within astronomy or physics.
The International Astronomical Union (IAU) 2006 definition established three categories: planets, dwarf planets, and small solar system bodies.3) Under this definition, eight planets are recognized; Pluto was reclassified as a dwarf planet. This classification is formally adopted by the IAU but remains contested within the planetary science community on definitional grounds - particularly the “clearing the neighborhood” criterion - making this a case of institutional consensus without full community consensus (see Limits and Open Questions).
Consensus exists on the broad architecture: terrestrial planets (Mercury through Mars), the asteroid belt, gas giants (Jupiter, Saturn), ice giants (Uranus, Neptune), the Kuiper Belt, and the inferred Oort Cloud. The existence of the Kuiper Belt is observationally confirmed. The Oort Cloud is inferred from long-period comet dynamics but has not been directly observed.
The Nice model and its variants propose that the giant planets underwent significant orbital migration early in solar system history, explaining the Late Heavy Bombardment and the current orbital architecture. This model is widely used and influential, but specific mechanisms and the reality of the Late Heavy Bombardment as a distinct cataclysm remain actively debated within planetary science.4)
The following questions remain open or actively contested within the relevant expert communities:
The following viewpoints challenge aspects of the consensus described above. Their inclusion here does not constitute endorsement or characterization of their validity.