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IAU terminology favors “small Solar System body,” while “minor planet” may still be used; “asteroid” is a subset commonly applied to inner Solar System minor planets.
Asteroid terminology and classification basics distinguish asteroids from other small Solar System bodies using both naming conventions and physical behavior. In modern usage, the International Astronomical Union (IAU) prefers the broad term “small Solar System body” for objects that are not planets, dwarf planets, or natural satellites; this category includes asteroids, comets, centaurs, trojans, and trans-Neptunian objects. Historically, the first discovered asteroid (Ceres) was initially treated like a planet, and the term “asteroid” was proposed because these objects looked star-like (moving points of light) rather than showing a planetary disk. Physically, an object is classified as an asteroid rather than a comet if it does not develop a coma/tail when warmed by solar radiation. The distinction is not always perfectly sharp: some bodies show a continuum of properties, and some objects can transition between comet-like and asteroid-like behavior as their volatile materials are depleted. Broad compositional classes commonly used for asteroids include C-type (carbonaceous), M-type (metallic), and S-type (silicaceous/rocky), reflecting differences in typical spectra and inferred makeup. In practice, “asteroid” is often restricted to inner Solar System minor planets such as main-belt asteroids, Jupiter trojans, and near-Earth asteroids, while more distant populations are often treated separately (e.g., centaurs and trans-Neptunian objects).
IAU terminology favors “small Solar System body,” while “minor planet” may still be used; “asteroid” is a subset commonly applied to inner Solar System minor planets.
Asteroids are distinguished from comets by the presence of a coma/tail caused by sublimation; however, observations suggest a continuum between asteroid-like and comet-like objects.
Asteroids are broadly grouped by composition into C-type (carbonaceous), M-type (metallic), and S-type (silicaceous/rocky) based on characteristic spectra.
A broad IAU category for objects in the Solar System that are neither planets nor dwarf planets nor natural satellites, including asteroids and comets.
A traditional term for Solar System objects that are not planets, dwarf planets, or satellites; it may still be used even though “small Solar System body” is preferred.
A minor planet-like object that orbits the Sun and does not show cometary coma/tail activity when warmed by solar radiation.
A cloud around a comet’s nucleus produced when near-surface ices sublimate due to solar heating.
An asteroid class typically associated with carbon-rich (carbonaceous) composition and characteristic spectra.
An asteroid class typically associated with silicaceous (stony/rocky) composition and characteristic spectra.
An asteroid class typically associated with metallic composition and characteristic spectra.
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