Neptune has no definite surface, only a layer of gas above a layer of ice and water. While the planet has a core of rock and metal, Neptune's mantle consists of an ocean that contains more than 10 times the mass of Earth.
Though it is only four times larger than Earth, Neptune is the third most massive planet, and its distance from the sun means temperatures on the planet are extremely cold.
The atmosphere is made from hydrogen, helium and small amounts of methane, which helps create Neptune's blue glow. These gases extend far into the planet's center, where they gradually transition into water, ammonia and methane ices.
The planet gives off 2.6 times more energy than it receives from the sun, and gradually increasing temperatures toward the surface of the planet mean that the rocky core can reach higher than 3,000 degrees Fahrenheit. Scientists have yet to discover why the center of Neptune is abnormally hot, while the rest of the planet is around -360 degrees.
Neptune is also known for having the fastest winds, which can reach 1,300 mph. The planet's mantle is said to power its strong magnetic field, and motions at the planet's center cause unusual weather patterns. Neptune has six reddish rings made up of ice and silicates.