Neptune is a distant planet with 13 moons that is so far from the Sun that astronomers on Earth did not detect it until 1846. Neptune's size dwarfs the Earth, but life as we know it could not exist there.
Giant World
Neptune is 30 times more distant from the Sun than Earth is, and it is so large that if it were a hollow sphere 60 planets the size of Earth would fit inside it.
Smallish Core
Although Neptune is 30,760 miles in diameter, it is thought that the planet's core, which scientists think comprises an inner core of molten rock and an outer core of melted ices, is no larger than the mass equivalent of the Earth.
Discovery
Neptune's discovery was the result of mathematical calculations by astronomers who plotted where a heavenly body would be to cause the discrepancies in the orbit of Uranus that scientists had noticed.
One Orbit
Neptune orbits the sun at an average of 2.77 billion miles from it, making it the eighth planet in the solar system. Since Neptune requires so long to complete a single orbit of the Sun--165 years--it will be 2011 before it completes a full orbit since its discovery in 1846.
Methane
The large amounts of methane gas present on Neptune absorb the red spectrum of light and give the planet its blue hue. The clouds in the atmosphere are more than likely methane crystals.
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