Pluto

Pluto is usually farther from the Sun than any of the eight planets; however, due to the eccentricity of its orbit, it is closer than Neptune for out of its orbit. Pluto crossed Neptune's orbit , made its closest approach September and remained within the orbit of Neptune until. This will not occur again until September . As Pluto approaches perihelion it reaches its maximum distance from the ecliptic due to its degree inclination.

Thus, it is far above or below the plane of Neptune's orbit. Under these conditions, Pluto and Neptune will not collide and do not approach closer than to one another. Pluto's rotation period is days, the same as its satellite Charon. Although it is common for a satellite to travel in a synchronous orbit with its planet, Pluto rotates synchronously with the orbit of its satellite. Thus being tidally locked, Pluto and Charon continuously face each other as they travel through space.

Unlike most planets, but similar to Uranus, Pluto rotates with its poles almost in its orbital plane. Pluto's rotational axis is tipped degrees. When Pluto was first discovered, its relatively bright south polar region was the view seen from the Earth. Pluto appeared to grow dim as our viewpoint gradually shifted from nearly pole on in to nearly equator on in. Pluto's equator is now the view seen from Earth.

During the period from through , Earth was aligned with the orbit of Charon around Pluto such that an eclipse could be observed every Pluto day. This provided opportunity to collect significant data which led to albedo maps defining surface reflectivity, and to the first accurate determination of the sizes of Pluto and Charon, including all the numbers that could be calculated therefrom.