Neptune is the eighth planet from the Sun and the outermost major planet in the solar system. Known for its deep blue color, it is a gas giant discovered in 1846 through mathematical predictions by Johann Galle and Urbain Le Verrier. Named after the Roman god of the sea, Neptune is about four times the size of Earth and 17 times its mass. Its atmosphere consists mainly of hydrogen, helium, and methane, which gives it its signature blue hue. Neptune also has a dynamic weather system, including the fastest winds in the solar system, and 14 known moons, with Triton being the largest.