16. Two of Jupiter's Galilean moons, lo and Europe, make a complete revolution around it
over the periods T1=1.77 days and T2 = 3.55
days. Knowing that lo revolves around Jupiter
at a distance of 421600 km, determine the
linear velocity of Europe's motion in its orbit.

Neptune is the eighth planet from the sun. it was the first planet to get its existence predicted by  mathematical calculations  before it was actually seen through a telescope on sept. 23, 1846. irregularities in the orbit of  uranus  led french astronomer alexis bouvard to suggest that the gravitational pull from another celestial body might be responsible. german astronomer johann galle then relied on subsequent calculations to   spot neptune via telescope. previously, astronomer galileo galilei sketched the planet, but he mistook it for a star due to its slow motion. in accordance with all the other planets seen in the sky, this new world was given a name from greek and roman mythology — neptune, the roman god of the sea.