<P> In astronomy, Kepler's laws of planetary motion are three scientific laws describing the motion of planets around the Sun . </P> <Table> <Tr> <Th> Astrodynamics </Th> </Tr> <Tr> <Td> </Td> </Tr> <Tr> <Th> Orbital mechanics </Th> </Tr> <Tr> <Td> Equations (hide) <Ul> <Li> Kepler's laws </Li> <Li> Tsiolkovsky rocket equation </Li> <Li> Vis - viva equation </Li> </Ul> </Td> </Tr> <Tr> <Td> Efficiency measures (show) <Ul> <Li> Payload fraction </Li> <Li> Propellant mass fraction </Li> <Li> Mass ratio </Li> </Ul> </Td> </Tr> <Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> </Table>

What law describes how a planet orbits the sun