Origin of the Solar System – Vocabulary Review

15 vocabulary flashcards covering ages, key terms, and major theories about the origin and evolution of the Solar System and Universe.

Age of the Universe

Approximately 13.8 billion years old.

Age of the Solar System

Roughly 4.5–4.6 billion years old, including Earth.

Solar Nebular Theory (Solar Nebular Hypothesis)

Model stating the Solar System formed from the gravitational collapse of a rotating interstellar gas-and-dust cloud (solar nebula), triggered perhaps by a nearby supernova, leading to a protostar (Sun) and a protoplanetary disk.

Interstellar Gas and Dust Cloud (Solar Nebula)

Diffuse mixture of hydrogen, helium, and dust whose contraction and rotation produced the Sun and planets.

Supernova Trigger

Explosion of a massive star whose shock waves may initiate the collapse of a nearby gas-and-dust cloud.

Accretion

Process by which tiny grains collide and stick together, growing into centimeter-, meter-, and kilometer-sized bodies.

Planetesimal

Kilometer-scale body formed by accretion; basic building block of planets.

Protoplanet

Large object produced by coalescing planetesimals; precursor to a full-sized planet.

Protostar

Dense, hot core formed at the center of a collapsing nebula that will ignite nuclear fusion to become a star.

Cartesian Vortex Theory (René Descartes)

17th-century idea that whirlpool-like motions in subtle matter organized the Sun, planets, and satellites into nearly circular orbits.

Collision Theory (Georges-Louis Leclerc, Comte de Buffon)

Hypothesis that a giant comet’s collision with the Sun ejected debris that condensed into planets all orbiting in the same direction.

Kant–Laplace Nebular Theory

18th-century model where a rotating gaseous nebula collapsed, flattened, and formed bulges that became the Sun and planets.

Jeans–Jeffreys Tidal Theory

Proposal that a passing massive star’s gravity ripped material from the Sun; the stripped matter later condensed into planets.

Angular-Momentum Problem

Early difficulty explaining why the Sun holds most mass yet little of the Solar System’s angular momentum; addressed by the Solar Nebular Theory.

Protoplanetary (Rotating) Disk

Flattened disk of gas and dust orbiting a protostar where planets, moons, and other bodies form.