Minor-planet moon

A natural satellite that orbits a minor planet, including an asteroid or trans-Neptunian object. Such systems range from a tiny companion to a nearly equal-mass binary.

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Binary asteroid: An asteroid system consisting of two bodies orbiting their shared center of mass. Many asteroid moons form systems whose two components have comparable sizes.
Dactyl: The small satellite of the asteroid Ida, photographed by the Galileo spacecraft in 1993. Its discovery provided the first direct evidence that an asteroid has a moon.
Giant impact hypothesis: The hypothesis that a large collision produced a body's orbiting debris or companion. Impact-generated debris is one proposed route to forming moons around minor planets.
DART (spacecraft): NASA's Double Asteroid Redirection Test spacecraft, which struck Dimorphos in 2022. The mission used a minor-planet moon to measure an impact-driven change in orbit.
Asteroid belt: The region between Mars and Jupiter containing most of the Solar System's known asteroids. Surveying this population helps establish how frequently main-belt asteroids have moons.
Rotational fission: The splitting of a rapidly rotating body into two or more gravitationally bound components. Rapid spin can shed material that gathers into a moon around an asteroid.
Dimorphos: The small moon of the near-Earth asteroid Didymos and the target of NASA's DART impact test. Its orbit provided a measured case of how a moon can respond to a deliberate impact.
Capture (astronomy): The process by which a body becomes gravitationally bound to another after passing through its vicinity. Capture may explain some irregular satellites, though permanent capture requires energy loss or interaction.
Hera (space mission): The European Space Agency mission designed to study the Didymos–Dimorphos system after DART's impact. Hera will characterize the crater and the system's physical properties after the deflection test.
Kuiper belt: A distant region beyond Neptune containing icy minor planets and other small Solar System bodies. Its many binaries raise questions about how outer Solar System moons formed and survived.