Double planet the four, small, outer satellites of Pluto. A now-abandoned hypothesis for the origin of the Moon was actually called the "double-planet hypothesis"; the idea was that the Earth and the Moon formed in the same region of the solar system's proto-planetary disk, forming a system under gravitational interaction. This idea, too, is a problematic condition for defining two bodies as "double planets" because planets can "capture" moons through gravitational interaction. For example, the moons of Mars (Phobos and Deimos) are thought to be asteroids captured long ago by Mars. Such a weak definition would also deem Neptune-Triton a double planet,
How Much for Just the Planet? How Much for Just the Planet? How Much for Just the Planet? is a 1987 "Star Trek" tie-in novel by John M. Ford. In the novel, large deposits of dilithium are detected on a colony planet, and delegations are sent by the United Federation of Planets and the Klingon Empire to negotiate for mining rights (neither able to openly fight against the other because of the "Organian Lightbulbs", a reference to the Organians from the original series). They find the planet Direidi and its inhabitants to be very strange indeed. Planet inhabitants occasionally break into song to explain their narratives