Formation and evolution of the Solar System

The Solar System formed about 4.6 billion years ago as gravity collapsed a cloud of gas and dust into the Sun and a surrounding disk. Accretion and later dynamical changes produced its planets, moons, asteroids, and comets.

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Solar nebula: The rotating disk of gas and dust surrounding the young Sun, from which Solar System bodies formed. Its collapse and structure supplied the material and setting for planet formation.
Snow line (astrophysics): The distance from a young star beyond which volatile compounds can condense as ice in a protoplanetary disk. Beyond this boundary, abundant ice helped planetary cores grow rapidly.
Carbonaceous chondrite: A primitive stony meteorite rich in volatile elements and often containing water-bearing minerals and organic compounds. Its relatively unprocessed material records the chemistry of the early Solar System.
Nice model: A model in which the giant planets migrated and underwent orbital instability, reshaping the outer Solar System. It explains how an initially compact giant-planet system could produce today’s distant populations.
T Tauri star: A young, low-mass star in a variable phase marked by strong activity and often a surrounding disk. Its winds and radiation help constrain how long the Sun’s planet-forming disk lasted.
Protoplanetary disk: A disk of gas and dust around a young star, where planets can form. The early Solar System was a protoplanetary disk in which solids accumulated.
Condensation sequence: The order in which minerals and volatile substances condense from a cooling gas, determined by temperature and pressure. It links disk temperatures to the distinct compositions of Solar System materials.
Murchison meteorite: A carbonaceous chondrite that fell in Australia in 1969 and contains diverse organic compounds. Its minerals and isotopes provide a detailed sample of primitive Solar System matter.
Grand tack hypothesis: A model in which Jupiter migrated inward and then outward after Saturn became trapped in an orbital resonance. It proposes a route to the small mass of Mars and the structure of the asteroid belt.
Disk instability model: A model in which a massive protoplanetary disk fragments under its own gravity to form giant planets. It offers an alternative to core accretion for the origin of giant planets.