Robert’s Out of This World Space Odyssey: Neptune, The Final Planet

Neptune is the 8th and outermost planet in our solar system (Pluto is no longer a planet and we will talk about that another time), orbiting 2.8 billion miles (4.5 billion kilometers) away from the sun. That makes Neptune far enough away for people on Earth not to be able to see it without a telescope. Even then it just looks like a fixed star. If you remember an older post, you will know that since Neptune is hard to see from Earth (impossible without a telescope), it is actually the first planet discovered using math. Two astronomers working in the mid-nineteenth century, John Couch Adams and Urbain Le Verrie, both realized that the orbit of Uranus was not as predicted – something with a large gravitational force must be altering it. It must be another planet. On September 23, 1846, Neptune was discovered and named after the Roman god of the sea (the international community of astronomers didn’t like naming the planet after Le Verrie).

Neptune is roughly 4 times bigger than Earth and is comprised mostly of hydrogen, helium, water and silicates (the stuff you make rocks out of). Like its sister ice giant, Uranus, Neptune has an inner rocky core (about the size of Earth), surrounded by a liquid layer that blends into layers of thick clouds. These clouds whip around the planet, sometimes at speeds greater than the winds on Jupiter. The clouds contain methane, which provides the planet’s brilliant blue color.

Being the farthest from the sun also means taking the most time to complete an orbit. One full year (a complete orbit around the sun) on Neptune takes 165 Earth years. One day on Neptune (full rotation around its axis) lasts 16 hours 7 minutes.

Neptune has 6 thin, hard to notice and non-uniform rings. It also has 13 identified moons. Triton is the largest moon and is the only major moon in the universe to orbit a planet in the opposite direction the planet rotates. It is believed that Triton started life as a comet orbiting the sun. One day it got a little too close to Neptune and before it realized what was happening; it got sucked into orbit by Neptune’s gravity and became a moon. The surface of Triton is the coldest known place in our solar system, coming in at a bone chilling -390°F (-235°C).

And that’s it. You have now learned a little something about all of the planets in our solar system. I hope you enjoyed our lovely little space odyssey!