Kepler 1) What is an astronomical unit? 2) Use Kepler's third law to determine the orbital period of Jupiter. Its orbital radius is 5.203 AU. (11.87 Earth years) 3) Pluto takes 90 553 Earth days to orbit the Sun. Use this value to determine its mean orbital radius. (39.465 AU) Satellites Neptune's average orbital radius is 4.50 x 1012m from the Sun. The mass of the Sun is 1.99 x 1030 kg. What is Neptune's orbital speed? (5.43 x 103 m/s) The moon Miranda orbits Uranus at a speed of 6.68 _ 103m/s. Use this speed and the mass of Uranus to determine the radius of Miranda's orbit. The mass of Uranus is 8.68 x 1025 kg. (1.30 x 108 m) The International Space Station orbits Earth at a height of 359.2 km. What is its orbital speed? (7.69 x 103 m/s)