As the eighth planet in the Solar System, and the furthest from the sun, Neptune is a great mystery to many. It is the third most massive planet, and it is 17 times the mass of Earth. Named after the Roman god of the sea, it takes Neptune almost 165 Earth years to orbit the sun, and it is about 4.5 billion kilometers away. When you look up into the sky with the naked eye, you cannot see Neptune. It is only visible with a telescope. In fact, the first time it was ever seen was on September 23, 1846. This was done by Johann Galle, and its location was actually predicted by another man, Urbain Le Verrier by using mathematical equations. When it was finally found, it was only about a degree away from the predicted location, which is very cool!
Remarkably, Neptune has a total of 14 moons. The largest, Triton, was discovered soon after the planet, itself. The other 13 moons were not discovered until later in the 20th century. Since the plant is so far away, it’s difficult to know if there are other moons, but thus far, none have been found. The planet has been examined by NASA, though, thanks to the Voyager 2, which flew near it in August 1989. We also are able to look at the planet with the Hubble Space Telescope and other large telescopes, which has helped us learn more about it. Are you ready for the top 10 facts about Neptune? Keep reading!
10Neptune is Almost All Hydrogen
Neptune is known as a “gas giant.” This is a name given to the four largest planets of the Solar System. Unlike the smaller planets, such as Earth and Mars, Neptune, Jupiter, Uranus, and Saturn are all made of gas. In the case of Neptune, it is made of about 80 percent hydrogen. The rest of the planet contains helium and very small amounts of methane. However, some call Neptune an “ice giant,” as it also has a lot of ice in its composition.
Speaking of methane, it’s the methane in the atmosphere of Neptune that gives it the blue color that we often associate with it. Uranus, it’s neighbor, has a similar phenomenon happening, but Neptune is a deeper shade of blue than Uranus. This is likely because there is another component in the atmosphere of Neptune that we are not quite aware of yet.
Though Neptune is made of gas, it does have a rocky core, which is similar in size to Earth. It is made of mostly iron, and even though the planet is very far from the sun, the center core is estimated to reach temperatures of over 9,000 degrees F. The center of the core is highly pressurized, about double the pressure found in the center of the Earth. It is also believed that the pressure is so high that the methane is turning into diamonds, which act like rain or hail.
9Neptune Has Two Different Weather Patterns
Here on Earth, we have a lot of different types of weather. It might rain, snow, hail, or be warm and sunny, depending on where you are on the planet. This is all because of how close we are to the sun. On Neptune, however, things are different. The planet is so far away from the sun, that it cannot possibly affect the weather. What actually does affect the weather is a big mystery, but there are two different weather patterns that we know of.
The first of these, which were first discovered by Voyager 2, are large dark spots. This might sound familiar to you if you know about the Great Red Spot, which is found on Jupiter. The main difference, however, is that the great storm which makes up the Great Red Spot has been going on for centuries, as far as we know, the dark spots on Neptune come and go. They were present, for instance, when the Voyager 2 flew by, but they had disappeared when viewed by the Hubble Space Telescope only a few years later.
The second weather pattern that we know is present on Neptune was also first discovered by the Voyager 2. It is a white storm system, which has been named “Scooter.” It is very swiftly moving, and as the dark spots, are also short-lived. We also know that Scooter moves in an eastward direction, as do the dark spots, and they all move at different speeds.
8Neptune Has Strange Rings
When we usually think of planets with rings, we think of Saturn. However, most people don’t realize that Neptune also has rings. There are five main rings that surround this planet, and they are not as solid, nor as visible, as Saturn’s rings. Instead, they are a bit clumpy and appear as if they have arcs in them. This is likely due to the gravitational pull of one of the moons of Neptune, but scientists can’t be sure of the exact reason. The rings are made of silicates, organic compounds, and particles of ice, and they are red in color.
The rings of Neptune were first discovered when astronomers were trying to study the planet through the lens of a microscope. They observed that as the planet passed by a star, it faded briefly, and then returned to view. In other words, the ring of Neptune hid the star for a moment so that it could not be seen. However, it wasn’t until Voyager 2 visited Neptune that we really got to see the rings close up.
Researchers believe that the rings of Neptune are pretty young when compared to the planet, itself. Additionally, the rings are much younger than those around Saturn, Jupiter, and Uranus, which all have rings, too. Scientists also believe that the rings were formed when a former moon of Neptune got too close to the planet and was totally decimated by its gravity.
7Neptune is…Controversially…the Furthest Planet from the Sun
When you say Neptune is the furthest planet from the Sun, you are sure to hear someone say, “Well, what about Pluto?” We will get to that in a moment… When discovered in 1846, Neptune was definitely, without controversy, the most distant planet in the Solar System…at least that we knew about. However, 84 years later, Pluto would be discovered, and Neptune was pushed on to be the second-most distant planet from the sun. Here’s where things get dicey, though. Pluto does not have a round orbit. It is actually elliptical, and it actually crosses Neptune’s orbit. This means that sometimes, every 248 years, to be exact, Pluto is closer to the sun than Neptune. This happens for about 20 years, and the last time it happened was from 1979 until 1999. This, however, is not why Neptune is officially the furthest planet from the sun.
In 2006, the General Assembly of the International Astronomical Union met in Prague, and it was decided after some new astronomical bodies were discovered, that the definition of a planet would be changed. Basically, the new definition of a planet was one that is gravitationally dominant and does not have any other bodies of comparable size. Pluto does not fit this meaning after it was found that these new astronomical bodies were similar in size to Pluto and acted similarly to it.
After this change in definition, Pluto was out, and instead called a “dwarf planet,” along with several other celestial bodies. So, that officially, once again, made Neptune the furthest planet from the Sun.
6Neptune Has the Strongest Winds in the Solar System and is Also the Coldest Planet
According to the Weather Channel, the strongest wind ever recorded on Earth was 295 miles per hour during a tornado in El Reno, Oklahoma. That sounds horrifyingly fast, and it is certainly deadly, but compared to the winds on Neptune, those terrifying tornado winds are just a cool breeze.
It is estimated that the winds on Neptune can get as high as 2,100 kilometers per hour, which is about 1,304 miles per hour. Scientists are quite puzzled about how a cold, icy, gas planet like Neptune can have winds so high, but it happens. One theory is that the frigid temperatures and the gasses in Neptune’s atmosphere might reduce typical friction, which affects wind speed. If this is the case, the winds would be able to move much more quickly. These are the strongest winds ever recorded in the Solar System.
Not only does Neptune hold the record for the strongest winds, though. It is also the coldest planet. This makes sense since it’s so far from the sun. The coldest temperature ever recorded on Neptune is -366.6 degrees F. The coldest temperature ever recorded on Earth was -129 degrees F. if a human would step onto the surface of Neptune…if it had a surface to walk on…that human would totally flash freeze in less than a second. Though Pluto gets colder, sadly, it’s no longer a planet, remember?
5The Discovery of Neptune is Also Under Controversy
It has already been mentioned that Neptune was first seen by Johann Galle in 1846, but it’s discovery isn’t as cut and dry as you might think. First, it is almost indisputable that Galileo would have been the first person to actually see Neptune. We know this because he marked its location on a drawing of the stars as he observed the Solar System. However, Galileo marked what we now call Neptune a star and not a planet. So, he does not get the credit for discovering it.
Now, here’s where things get interesting. We know that Neptune cannot be seen with the naked eye, so mathematicians had to make very educated guesses about where potential planets might be. There were two, Urbain Le Verrier, a French mathematician, and John Couch Adam, an English mathematician, who both calculated that there was a new planet beyond Uranus, which was discovered in 1781.
Known as Planet X, this proposed new planet would be, based on their calculations, in a very specific region in the sky. Johann Galle used these calculations to search that region, and he did finally find it, only one degree from the proposed location. Both of the mathematicians claimed that they should get credit for discovering Neptune, and they battled over it for a long time. In fact, even today, there are still those who are in the “Adams Camp” or the “Le Verrier Camp,” and the arguments continue. In general, however, it is said that both Adams and Le Verrier should get equal credit for discovering Neptune.
4The Gravity on Neptune is Earth-Like
Whenever we talk about different planets, one of the first things that people wonder is what the gravity is like. We know that here on Earth, the pull of gravity helps us to keep our feet on the ground. We don’t feel it, nor does it really physically affect us. The gravity on Earth is about 1 g, and the gravity on Neptune is 1.14 g.
Remember, Neptune is a ball of ice and gas with a rocky core, so you couldn’t really walk on it. Instead, you would just sink into it if you tried. If, however, it was possible to stand on Neptune, it would feel almost exactly the same as if you tried to walk on Earth. The gravity on Neptune is only 17 percent stronger than it is on Earth. However, it also has 17 times the mass of Earth. On top of that, Neptune is about four times larger than Earth. This allows the mass to be spread out over the large volume of the planet, so at the surface, it’s almost the same.
Though if we could stand on Neptune, we would barely notice, not all planets are the same. Theoretically, the human body could survive three or four times the gravity we have now, but we would all have to be pretty athletic in order to walk. The planet with the strongest gravity is Jupiter, and even that is only about four times the gravity on Earth.
3Neptune Probably Captured Triton
The largest, and most well-known, of Neptune’s moons is called Triton. It’s a pretty interesting satellite, too. First, it circles Neptune in an orbit that is actually backward, or retrograde, when compared to the planet’s other moons. This is really unusual, but it does tell us something about Triton…the moon was probably captured by Neptune, and it did not form alongside the planet like the others.
To make things even more interesting, Triton moves in rotation with Neptune, and it is slowly, but surely, moving closer to the planet. This means that at some point, likely billions of years from today, that Triton will be ripped apart by Neptune’s gravitational force. Do you know what will happen, then? It will become another ring, just like those that are there now.
We can’t stop there with Triton, though. Remember, above, how we said that Pluto was part of a group of similar planets? Guess where scientists believe Triton came from? If you guessed that same group, you are right. This means that we could say Triton is just as much of a dwarf planet as Pluto is, except for the fact that it got plucked out of the Solar System by Neptune many, many years ago.
Triton also has an interesting and fitting name. You see, Neptune was named after the Roman god of the sea. The Greek’s also had a god of the sea, whom they called Poseidon. Now Poseidon had a son, who was named…you guessed it…Triton. So, it’s almost like those astronomers saw this moon as the son of Neptune, though now, we know that there are many moons and that Triton is probably not associated with Neptune, at all. Instead, Neptune captured it.
2There Has Only Ever Been One Visit to Neptune
Since its discovery, there has ever only been one visit to Neptune. This, of course, was the Voyager 2 spacecraft, which was sent by NASA. The Voyager 2 was sent into orbit on August 20, 1977, and it finally flew by Neptune on August 25th, 1989, more than 12 years later.
During the visit, which is best described as a fly-by, Voyager 2 was able to get a ton of information on Neptune. It collected data on Neptune’s rings, its atmosphere, the Great Dark Spot, and even got a good, close look at Triton. Additionally, the satellite discovered six new moons around Neptune, which we had no idea even existed.
On top of this, Voyager 2 was able to take a number of photographs, of both Neptune and Triton, and we could finally see some remarkable features of both. This includes a large ice volcano on the surface of Triton and it discovered the strange weather systems and extreme temperatures and winds on Neptune.
Today, Voyager 2 is still floating out there in space and sending information back. Currently, only five of its instruments are still working, and eventually, it will run out of power, but for now, we can still rely on the information it sends.
1 There are No Plans to Go to Neptune Again
Though we can look back fondly at the information Voyager 2 gave us about Neptune, and we now have access to tools such as the Hubble Telescope, that might be all we get for a while. As of now, there are no plans to return to Neptune, and even if something, like another Voyager mission, was put into motion, it would likely be more than a decade before it arrived.
There were some tentative plans by NASA to send out a new mission towards Neptune in the late 2020s or even early 2030s, but thus far, nothing has really come from that. There was also an attempt in 2003 to send a mission to Neptune known as the Neptune Orbiter. This was supposed to launch in 2016 and would be scheduled to arrive at Neptune in 2030. The mission’s plan was to look at the rings, the moons, and the weather of Neptune. However, there was never any more information released to the public about the project, so it is thought that it was, at some point, scrapped.
On top of this, NASA proposed that it would send a spacecraft called Argo into orbit at some point in 2019. The plan for this mission was to visit Jupiter, Saturn, and Neptune, where it would also take a close look at Triton. However, the craft requires Plutonium-238 as its power source, and the US has not produced this since 1988. Russia did have some available for purchase, but it, too, has reportedly stopped producing it. So, for now, there are no plans for any future visits to Neptune.
Neptune is certainly one of the most mesmerizing planets in our Solar System. It remains a cryptic puzzle for the most part, but we know enough about it to make us even more curious about the mysteries it holds. Neptune is a fascinating planet and certainly worthy of study. It is stunning to look at in the photos we have, and it continues to captivate amateur and professional astronomers, alike.
Since we know that NASA, nor any other organization, currently has plans to visit Neptune anytime soon, we must rely on the information we get from other sources. For instance, the Hubble Telescope continues to discover data about Neptune, and NASA posts all new information on the website, Hubblesite.org. Just this year, there has been a possible new moon discovered orbiting Neptune, and a new, raging storm system was found.
So, even though we can’t necessarily get a satellite or spacecraft up close and personal with Neptune, there is still a lot that we can learn down here with our feet planted firmly on Earth. Only time will tell when these mysteries of the planet will be unraveled, but for now, let’s revel in its beauty and secrets.