Solar eclipse from Jovian moon. Artwork of a solar eclipse seen from Callisto, a large moon orbiting the planet Jupiter. The Sun is being eclipsed by Jupiter (centre left) as Callisto passes into the Jovian shadow. This is seen from Earth as Callisto fading from the night sky. Callisto takes 16.5 Earth days to orbit 1.9 million kilometres from Jupiter. Callisto and is one of the four Galilean satellites, of which Ganymede and Io (upper right, crescents) are also seen. Eclipses of these Galilean moons are observed by Earth telescopes as an important way of checking theories on orbital mechanics.