These facts about Neptune offer an insight to the eight planet from the Sun. You may need this insight becuase it is invisible to the naked eye due to its great distance from the Earth. Telescopes reveal a small bluish – green disk for this gas giant..
Interestingly, Neptune was first discovered by mathematical computations, then by actual observation. Astronomers first suspected that there was another planet because Uranus moved strangely in its orbit. By 1845, the difference in the mathematical position and the actual observed position of Uranus strongly suggested that an unknown planet was orbiting beyond Uranus.
2. Orbiting the Sun
Neptune is far from the Sun at a mean distance of 2.794 billion miles. It takes the planet almost 165 years to complete one orbit around the Sun at an orbital velocity of 3.4 miles per second. The planet’s orbit is nearly a perfect circle with only a very small tilt to the plane of the ecliptic.
3. 15 hour days
Studies of the planet’s atmosphere reveal that the planet rotates on its axis in 15 hours and 48 minutes, giving Neptune the longest day of all four of the gas giants. Its axis is tilted at an angle of a little less than 29 degrees. There is very little seasonal difference between its summer and winter, with the mean temperature, at the top of its clouds, a chilly -350 degree F.
Neptune is the almost identical twin of Uranus. Like the other gas-giants planets, the major portion of Neptune’s mass is made up of a deep hydrogen and helium atmosphere. Beneath this thick cloud cover lies a liquid water mantle surrounding a hot rocky core. Neptune is the densest of all the gas-giants with a mean density of .33 times that of Earth. It would take 57 Earths to fill the space occupied by Neptune and 17.2 Earths to equal its mass.
5. The moon spins backwards
Triton is the only major satellite in the Solar System that orbits opposite to the spin of its parent planet. Scientists believe that Triton was once a free object in the Solar System and was captured by Neptune. Voyager’s cameras found a great variety of terrain on Triton. There are regions of large, flooded impact craters, rolling terrain with light cratering, and mysterious markings that resemble cantaloupe skin in other areas.