<Tr> <Th> Semi-major axis </Th> <Td> 30.11 AU (4.50 billion km) </Td> </Tr> <Tr> <Th> Eccentricity </Th> <Td> 6997945600000000000 ♠ 0.009 456 </Td> </Tr> <Tr> <Th> Orbital period </Th> <Td> <Ul> <Li> 164.8 yr </Li> <Li> 60,182 days </Li> <Li> 89,666 Neptunian solar days </Li> </Ul> </Td> </Tr> <Ul> <Li> 164.8 yr </Li> <Li> 60,182 days </Li> <Li> 89,666 Neptunian solar days </Li> </Ul>

What is the surface of neptune made from