Last Call

7th planet from the Sun is Neptune, named after the Roman God of the Seas. Galileo discovered it as a star when it was close to Jupiter, it was reconsidered in the 19th century. It was predicted by scientists before it was spotted. They guessed this because something was pulling at Uranus to leave its orbit. The location it was found as a planet was close to where Galileo found it in 1846.
Voyager 2 has visited Neptune & sends information about it since 1989. Voyager 2 has been sending the most information in our Solar System. Very similar composition to Uranus, both Ice Giants because of large quantities of hydrogen. Small, rocky core. Atmosphere=74% hydrogen, 25% helium with trace amounts of methane, carbon, oxygen & nitrogen. Methane gas is responsible for its blue colour, it absorbs the red spectrum of light. Another unknown substance to enhance colouring.
1 day on Neptune is 16 Earth hours, 1 year is 165 Earth years. Voyager 2 visited it in1989, photographed a dark spot like Jupiter's Red Spot. Thought to be similar hurricane-like storm, winds of 2,414.016km/h. 1994, Hubble Space Telescope (HST) tried to take a photo of the Great Dark Spot, it had disappeared! Another 1 was crater farther north than the original, Northern Great Dark Spot.
Neptune has 13 known moons, largest=Triton. William Lassel discovered Titan in 1846, the only known moon to orbit its planet retrograde. While the planet moves in 1 direction, Triton moves in the opposite. Triton is slightly smaller than our Moon, has an elliptical orbit & frictional resistance, pushing & stretching Titan.
Neptune's friction with its moon has created a warm inner core, because of this, there is ice volcanoes & frozen lakes. Triton has a thin nitrogen atmosphere: most moons are too small.
4 rings made of dust, ice particles & sand surround Neptune. Thought to be made by satellites crashing and throwing debris everywhere. The outermost ring has bright arcs thought to be caused by its moon, Galatea's gravitational interference with the ice particles, causing them to clump together.

Pluto is a planet that is not a planet, named after the Roman God of the Underworld. How is a planet not a planet? The International Astronomical Union (IAU), changes there classification rules of planets regualarly. 2006, 3 rules to decide a planet: a. Must orbit around the Sun. b. Has a sufficient graviational pull on itself that keeps it spherical. c. It cleared its orbit of any other debris.
Pluto lost its definition as a planet because it didn't meet the last criteria. Considered a "dwarf planet."
Scientists predicted a "Planet X" before Pluto was discovered in 1930. Clyde Tombaugh discovered it. An 11-year old girl from England chose the name.
Might be like Triton, 70% rocky material & 30% ice. Low pressure, atmosphere=nitrogen, methane & carbon monoxide. 1/6th the mass of our Moon.
Pluto sometimes crosses orbits with Neptune. Temperature from -237.15 degrees Celsius to -235.15 degrees Celsius.
Pluto has 5 satellites. Most famous is Charon, the ferryman who carried souls across the River Archeron to the Underworld. Charon was discovered in 1978. Nix, Hydra, Kerberos & Styz were discovered in the 21st century. Charon's orbit is weird, both planet and moon onty present 1 face to each other at all times, could be double-dwarf planet.
No spacecrafts have visited Pluto. New Horizons is expected to reach it in 2015. It will take photos of the planet before heading off to the Kuiper Belt.