What is a minor-planet moon?
A minor-planet moon is a natural satellite that orbits a minor planet. As of the latest count, 625 minor planets are known or suspected to have such companions.
Questions about Minor-planet moon
Short answers, pulled from the story.
When was the first asteroid moon confirmed?
The first confirmed asteroid moon was discovered in 1993 when the Galileo probe found the small body Dactyl orbiting the asteroid 243 Ida in the asteroid belt. The second confirmed moon was found around 45 Eugenia in 1998.
What is the largest known minor-planet moon?
The largest known minor-planet moon in absolute size is Charon, which orbits Pluto and has a diameter roughly half that of Pluto. Charon is large enough that the two bodies orbit a shared barycenter located outside Pluto's surface.
Why do scientists study minor-planet moons?
Measuring a moon's orbit allows scientists to calculate the mass and density of the primary body, revealing physical properties that are generally not otherwise accessible. Density in particular indicates whether a minor planet is solid rock or a loosely bound aggregate.
How common are binary minor planets?
Among asteroids overall, an estimated 2% are thought to have satellites. Among trans-Neptunian objects the proportion rises to roughly 11%, and the majority of large trans-Neptunian objects have at least one moon.
What is the most complex known minor-planet system?
The most complex known minor-planet systems are the Pluto sextuple system, with five moons including Charon, Nix, Hydra, Kerberos, and Styx, and 130 Elektra, a quadruple asteroid discovered with three moons in 2021, the only known quadruple asteroid.