Short answers, pulled from the story.
Neptune was directly observed through a telescope on the 23rd of September 1846 by Johann Gottfried Galle at the Berlin Observatory. He found it within a degree of the position predicted mathematically by Urbain Le Verrier, who shares discovery credit with John Couch Adams.
Neptune is called an ice giant because it is smaller than Jupiter and Saturn and carries higher concentrations of volatiles such as water, ammonia and methane. Its mantle, worth 10 to 15 Earth masses, is rich in these ices, a label it shares with Uranus.
Neptune has the strongest sustained winds of any planet in the Solar System, reaching almost 600 metres per second, faster than the speed of sound. These winds are fueled by internal heat, as Neptune radiates about 2.61 times as much energy as it receives from the Sun.
Neptune was named after the Roman god of the sea, identified with the Greek Poseidon. Urbain Le Verrier proposed the name, and Struve endorsed it on the 29th of December 1846 before the Saint Petersburg Academy of Sciences, after the planet's color seen through a telescope.
Triton is Neptune's largest moon, holding more than 99.5 percent of the mass orbiting the planet. William Lassell discovered it just 17 days after Neptune itself, and its retrograde orbit indicates it was captured, probably once a dwarf planet from the Kuiper belt.
Voyager 2 is the only spacecraft to visit Neptune, making its closest approach on the 25th of August 1989. Signals took 246 minutes to reach Earth, and the flyby measured Neptune's mass, discovered six new moons, and revealed more than one ring.
Neptune orbits the Sun once every 164.8 years at an orbital distance of 30.1 AU. On the 11th of July 2011, it completed its first full barycentric orbit since its discovery in 1846.