Hobbies And Interests
Pluto
According to NASA documentation, Pluto is about two-thirds the diameter of the Earth's moon and takes 248 years to orbit the sun. As Pluto orbits the sun it spins on its side; in other words its equator is nearly at right angles with its orbit.
Charon
Charon was discovered by James Christy in 1978. It is made up of rock and ice like Pluto; it is also of a similar size, and orbits very close to Pluto. Due to these factors, scientists sometimes refer to Charon and Pluto as being a double planet. Moreover, according to Windows to the Universe, some scientists believe Charon was formed when a large object crashed into Pluto.
Charon and Pluto
Charon orbits Pluto around its equatorial plane. Thus the axis of its orbit and its rotation pole are tipped and lie in the plane of Pluto's orbit around the sun. Charon, like Earth's moon, spins around in exactly the same amount of time it takes it to orbit Pluto, meaning you would only every see one side of it. However, Pluto also spins at the same speed as Charon, meaning that on one half of Pluto, Charon is always up in the sky, whereas the other half will never see it. Thus, the phases of Charon are only visible on one side of Pluto.
Phases of Charon
A single orbit of Charon around Pluto takes 6.4 days. During this period the quickest change in phase occurs. When the sun is directly over the equator, the "new moon" of Charon is directly in front of the sun, producing an eclipse. Then as Charon continues in its orbit, it progresses through the same phases Earth's moon exhibits every month, but taking only 6.4 days to complete the cycle. Another longer term cycle that affects the phases of Charon, occurs as Pluto orbits the sun. The only period when a full moon is visible is during the start of spring or fall. In contrast, at the start of spring or summer, only a little over half the surface of Charon is visible at its fullest.
Nix and Hydra
Pluto's two other, much smaller moons, are called Nix and Hydra. These are farther away from Pluto than Charon. These additional moons were discovered in 2005 by scientists using the Hubble Telescope. At the time of writing, information about the phases of these moons is unavailable. Moreover, the small size of Pluto and its moons, combined with the distance they are from the Earth, makes them extremely difficult to observe.