billion years old.
2.Jupiter has 63 _____.The largest, Ganymede, is bigger
than Mercury.3.The stars in the Milky Way, the ______ to which the sun belong, number in hundreds of billions.
4.The gas tail of a _____ always points away from the sun.
5.The first communications______ orbited the earth every 2 hours and 37 minutes.
planets
moons
comet
galaxy
solar system
satellite
