Callisto, after mythological characters associated with Zeus, the Greek counterpart of the Roman god Jupiter. These four moons of Jupiter are now known as the Galilean satellites.
    Galileo’s observations of the Jovian satellites provided strong evidence supporting the view that the Sun rather than the Earth was the center of the solar system. Galileo observed these satellites revolving around Jupiter in a regular pattern, which contradicted the then-prevalent Ptolemaic theory that everything in the solar system revolved around the Earth. His observations suggested that the planets of the solar system, includ- ing both the Earth and Jupiter, might revolve around the Sun.
    The Jovian satellites were also an