Solar System

The Sun and the bodies gravitationally bound to it, including planets, moons, dwarf planets, asteroids, and comets. Its structure reflects the formation and ongoing evolution of a star system.

Sun: The star at the center of the Solar System, whose gravity binds its members and whose radiation supplies most of their energy. Its mass dominates the system and anchors the orbits of every planet.
Gravity: The fundamental interaction by which masses attract one another and influence the motion of matter and light. Mutual gravitational attraction shapes planetary orbits and the system’s large-scale structure.
Solar nebula: The rotating cloud of gas and dust from which the Sun and Solar System formed. Its collapse and flattened disk supplied the raw material for the Sun and planets.
Voyager program: NASA’s twin-spacecraft mission launched in 1977 to study the outer planets and continue into interstellar space. The spacecraft transformed knowledge of the giant planets and later sampled the outer heliosphere.
Planet Nine: A hypothetical distant planet proposed to explain patterns in the orbits of some trans-Neptunian objects. Its existence remains unconfirmed, and searches have not yet found it.
Planet: A large, nearly round body that orbits a star and has cleared its orbital neighborhood of comparable objects. Eight planets make up the system’s most prominent orbiting bodies.
Orbital resonance: A relationship in which orbiting bodies repeatedly exert gravitational influence at regular intervals because their orbital periods form a ratio of small integers. Resonances organize moon systems and sculpt gaps and groupings among small bodies.
Protoplanetary disk: A rotating disk of gas and dust surrounding a young star, where planets can form. The Solar System’s early disk set the conditions for planet formation.
Jupiter: The Solar System’s largest planet, a gas giant with a massive atmosphere and an extensive system of moons. Its gravity strongly influences the orbits of small bodies across the system.
Oort cloud: A hypothesized distant, roughly spherical reservoir of icy bodies surrounding the Solar System. Its existence is inferred chiefly from the paths of long-period comets, not direct observations.

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