Additional Data:

Diameter:	49.244 km
Average distance to the sun:	4.495.000.000 km
The mass of 1 kg weighs on Neptun:	1.400 g
One year on Neptun lasts:	164 years 288 days
One day on Neptun lasts:	15 hours 58 minutes
Temperature on the surface:	-201 °C
Orbital velocity:	5,43 km/s
Orbital inclination:	1,7692 °
Orbital excentricity:	0,0113
Weight:	17 earth masses
Density:	1.638 kg/m³
Gravitational accelleration:	11,15 m/s²
Escape velocity:	23,5 km/s
Tilt of the rotational axis:	28,32 °
Number of moons:	14
Number of rings:	7

 

The history of the discovery of Neptune began with the discovery of Uranus. Once enough observational data had been collected to calculate the orbit of Uranus, a problem arose. The calculated trajectory deviated significantly from the observed trajectory. One possible explanation for this deviation was that Uranus is being deflected in its orbit by another heavy celestial body. In the mid-19th century, two mathematicians and astronomers, John Couch Adams and Urbian Le Verrier, independently predicted where the presumed eighth planet would have to be. At first, however, they were met with skepticism from the astronomical world about this prediction, but in 1846 Johann Gottfried Galle and Heinrich d'Arrest found the planet. It was very close to the predicted location. Unlike Uranus, this planet was very quickly named after the Roman god of the sea, rivers and earthquakes – Neptune.

Neptune is the second planet to be discovered in modern times. At 30 times the distance of the Earth from the Sun, it is so far away that 900 times less light per area reaches it than the Earth. It cannot be seen with the naked eye. To find it, you need a good pair of binoculars or a telescope and a star map with its position. After calculating its orbit, it could only be observed for a long time through earthbound telescopes. It wasn't until the flyby of Voyager 2 in 1989 that new insights were discovered.

Neptune, like Uranus, is one of the ice giants. These planets are similar in size to gas giants, but they are not only made up of gases, but have high proportions of water ice, ammonia and other compounds. Neptune has a layered structure and has the largest rocky core of all gas planets. Above its core is a layer of liquid hydrogen compounds, oxygen and nitrogen, which in turn is followed by a layer of liquid hydrogen with traces of helium and methane. Its atmosphere consists of 80% hydrogen, 19% helium and traces of methane and ethane. Its blue-green coloration is darker than Uranus's, which is probably due to more components than just methane. Although a very leisurely weather pattern was assumed at this distance from the Sun, Voyager 2 provided images of storms with wind speeds of up to 2,100 km/h. This means that Neptune is home to the strongest storms in the solar system.

Now that Pluto is one of the dwarf planets, Neptune is the outermost planet in our solar system. It takes about 165 years to complete one orbit around the sun, which means that in 2011, Neptune completed its first full orbit since its discovery.

So far, 14 moons and 7 rings are known around Neptune. The moon Triton was discovered shortly after Neptune itself. It was not until 1949 that the 2nd moon of Neptune, Nereid, was found. In 1989, six more moons were discovered with Voyager 2, and another five were found in 2003 by observations with ground-based telescopes. The discovery of its rings is also thanks to the Voyager probe.

Neptune's largest moon was discovered just 17 days later by William Lassell and named after Triton, the mythological son of Neptune. The name was slow to catch on in common parlance, as the moon, similar to the Earth's moon, was for a long time only referred to as the "moon of Neptune". With a diameter of 2,707 km, Triton is almost as large as the Earth's moon and has one of the highest reflectivity’s. As a result, it appeared much larger until the flyby of Voyager 2. Its surface is very smooth and consists of 25% water ice mixed with rock. It has a thin atmosphere of nitrogen and geysers, which also emit nitrogen. The temperature on its surface is -235 °C, which is just above absolute zero. Triton orbits Neptune retrograde, suggesting that it was captured by Neptune and did not form together with the planet.