Asteroid

An asteroid is a small rocky or metallic body that orbits the Sun. Most are in the asteroid belt between Mars and Jupiter.

Asteroid belt: A region between Mars and Jupiter containing most of the Solar System’s known asteroids. It is the main region where asteroids are found.
Keplerian orbit: An idealized orbit governed by gravity in which one body follows a conic path around another. It provides the basic model for an asteroid’s path around the Sun.
Solar System formation: The process by which the Sun, planets, and smaller bodies formed from a collapsing cloud of gas and dust. Asteroids are surviving remnants of the material from which planets formed.
Hayabusa2: A Japan Aerospace Exploration Agency mission that returned samples from the asteroid Ryugu to Earth. Its samples provide direct evidence about an asteroid’s composition and history.
Ceres (dwarf planet): The largest object in the asteroid belt and the only dwarf planet located there. Ceres shows how a belt object can be large enough to qualify as a dwarf planet.
Minor planet: A Solar System body that orbits the Sun but is not classified as a planet or comet. Asteroids are commonly classified as minor planets.
Orbital resonance: A configuration in which orbiting bodies exert regular gravitational influence because their orbital periods have a simple ratio. Resonances with Jupiter create gaps and shape asteroid-belt populations.
Protoplanetary disk: A rotating disk of gas and dust surrounding a young star, where planets and smaller bodies form. Asteroids originated as solid material in the Sun’s early disk.
OSIRIS-REx: A NASA mission that collected samples from the near-Earth asteroid Bennu and returned them to Earth. Its returned material enables laboratory study of a primitive asteroid.
Vesta: A large differentiated asteroid in the asteroid belt with a basaltic surface and a massive impact basin. Vesta preserves signs of internal melting and a complex impact history.

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