Science & Technology

Exploring the solar system’s mysterious blue giant.

The eighth planet from our sun, Neptune, is a giant swirly ball of ice and wind, unlike any other world in our solar system. So much remains unknown about what is now considered the most distant planet in our system. It’s so far away that not only is it invisible to the naked eye, unlike many of our neighboring planets, but also wasn’t even discovered by telescope until its existence was determined by theoretical math.

A World Far, Far Away

In the 1800s, astronomers noticed that Uranus, the seventh and farthest out planet known at the time, wasn’t moving in a way that made sense when compared to other planetary orbits. Two scientists, John Couch Adams of England and Urbain Le Verrier of France, realized something very big must be influencing the orbit and used math to calculate where the mysterious other planet must be.

Using their calculations, Johann Galle of Germany pointed his telescope in the right direction and officially discovered Neptune. Uranus was discovered on March 13, 1781, and Neptune’s discovery didn’t happen until Sept. 23, 1846. That’s a gap of more than 64 years, but that amount of time makes sense if we consider just how far away the planet really is. On average, Neptune is 2.8 billion miles from Earth (roughly 30 times farther from the sun than we are), whereas Uranus is only about 1.6 billion miles away. That means Neptune is almost as far beyond Uranus as Uranus is from us.

Voyager 2 took almost nine-and-a-half years to reach Uranus but almost 12 years to reach Neptune. As well as being farther away than Uranus, Neptune is also smaller. It’s still considered a giant — being the fourth largest planet in our solar system behind Jupiter, Saturn, and Uranus  — but its smaller size and greater distance still make it harder to find.

While Jupiter and Saturn are gas giants, Uranus and Neptune are ice giants, made up of heavier elements such as water, ammonia, and methane surrounding a rocky core. Neptune is about four times wider than Earth, with a diameter of 30,775 miles, and its mass is estimated to be 17 times that of Earth.

Neptune is host to 14 known moons – one of which rotates backward. A single rotation of the planet takes about 16 hours, though it’s not quite even. The equator spins slower, about 18 hours for one Neptune day, while the poles make the trip in about 12. The day may be shorter than on Earth, but the year is far longer. It takes Neptune about 60,190 Earth days – or 165 Earth years – to make one revolution around the sun.

Neptune – World of Wind and Mystery

Though we’ve known of its existence for almost 180 years now, Neptune remains a planet of mystery. To date, there has been only one mission to this faraway world. In 1989, the Voyager 2 probe flew by and sent back a wealth of data – but it left some questions unanswered and raised even more.

Neptune is a world of wind. Wind speeds have been clocked at 1,640 feet per second – about 1,118 miles per hour – which is more than 1.5 faster than the speed of sound. We have few real ideas as to why. But what’s even stranger is that these winds are blowing westward, or backward to the rotation of the planet.

As well, Neptune has a magnetic field that is offset from the center of the planet and changes from one rotation to the next because of this misalignment. Amy Simon, a senior scientist for planetary atmospheres at the NASA Goddard Space Flight Center, told Space.com: “We have no idea how you even do that.” She added, scientists also want to know why Neptune generates so much heat and why a couple of dark spots discovered on the planet in recent years have later seemingly disappeared.

Mythology and Music

The planet gets its name from Neptune, the ancient Roman god of the sea. The Greek version was Poseidon. Both were believed to rule the oceans and stir up mighty storms. The planet’s watery blue color is likely the reason behind the choice.

In 1916, English composer Gustav Holst composed his compilation titled The Planets. Neptune was the final of the seven suites. Holst imagined it just as many others did, and still do, as a mysterious, distant world. “Neptune, the Mystic” uses soft sounds and even a hidden choir to create a feeling of wonder and secrecy – a fitting depiction for the planet we probably know the least about.

1. Neptune is the eighth planet from the sun and is the last planet in the currently accepted model of our solar system.
2. Neptune was discovered by mathematical calculation before it was ever found with a telescope.
3. Neptune is a mysterious world with many unexplained features, like super-fast wind that blows in a contrary direction and an offset magnetic field.