Neptune is an intriguing planet. However, there is still a lot that people don’t know about it. Perhaps it’s because Neptune is the farthest planet from our Sun, or because there have been so few exploration expeditions so far out into our Solar System. Neptune is a gas (and ice) giant full of wonders, regardless of the reason!
We’ve collected a list of ten fascinating facts about this planet below. You may be familiar with some of them. Others, on the other hand, are certain to surprise and perhaps even astound you. Enjoy!
1. Neptune is the most distant planet in the solar system. This may appear to be a simple statement, but it is actually quite complex. Neptune was the most distant planet in the Solar System when it was discovered in 1846. However, Neptune became the second-most distant planet once Pluto was found in 1930.
Pluto’s orbit, however, is extremely elliptical, and there are times when Pluto is closer to the Sun than Neptune. This happened the previous time in 1979, and it continued until 1999. During that time, Neptune was once again the furthest planet.
The subject of which planet was the most distant was revisited at the XXVIth General Assembly of the International Astronomical Union, which took place in Prague from August 14th to August 25th, 2006. With the finding of multiple Pluto-sized worlds in the Kuiper Belt, including Eris, Haumea, Sedna, and Makemake, as well as the ongoing case of Ceres, the International Astronomical Union (IAU) determined it was time to come up with a precise definition of what a planet was.
The IAU passed a resolution that defined a planet as “a celestial body orbiting a star that is huge enough to be rounded by its own gravity but has not cleared its nearby region of planetesimals and is not a satellite” in what would prove to be a highly contentious decision. It must have enough mass to overcome its compressive strength and attain hydrostatic equilibrium, to put it another way.”
Pluto was “de-classified” as a planet as a result of this, and was reclassified as a “dwarf planet” instead. As a result, Neptune has reclaimed the title of the most distant planet. At least for the time being…
2. Neptune is the smallest of the Gas Giants: Neptune is the smallest of the Gas Giants. Neptune is the smallest gas giant in the Solar System, with an equatorial radius of approximately 24,764 kilometers, dwarfing Jupiter, Saturn, and Uranus. But here’s the kicker: Neptune is actually 18% larger than Uranus. Neptune has a substantially higher density than Uranus because it is smaller yet more massive. Neptune is the densest gas giant in the Solar System, with a density of 1.638 g/cm3.
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3. Neptune’s Surface Gravity Approaches That of Earth: Neptune is a gaseous and icy planet with a likely rocky core. There’s no way you’d be able to stand on Neptune’s surface without sinking in. However, if you were to step on Neptune’s surface, you would observe something incredible. The force of gravity dragging you down is nearly identical to the force of gravity you experience while walking on Earth.
Neptune’s gravity is only 17 percent stronger than that of Earth. That’s the closest thing in the Solar System to Earth’s gravity (one g). Neptune is 17 times the mass of Earth, yet it is also about 4 times the size. This means that its greater mass is distributed across a bigger volume, and the gravitational pull at the surface would be about comparable. Except for when you couldn’t seem to stop singing!
4. Neptune’s Discovery is Still a Controversy: Neptune was most likely first spotted by Galileo, who drew it as a star in one of his sketches. He is not credited with the discovery because he did not recognize it as a planet. That credit goes to Urbain Le Verrier, a French mathematician, and John Couch Adams, an English mathematician, who both predicted that a new planet, known as Planet X, would be discovered in a specific location in the sky.
Both mathematicians claimed credit for the discovery when astronomer Johann Gottfried Galle discovered the planet in 1846. English and French astronomers fought about who made the discovery first, and supporters of each claim may still be found today. Today, astronomers agree that Le Verrier and Adams are equally responsible for the discovery.
5. Neptune possesses the Solar System’s Strongest Winds: Do you think a hurricane is terrifying? Consider a storm with winds of up to 2,100 kilometers per hour. As you might expect, scientists are baffled as to how an incredibly cold planet like Neptune manages to change its cloud tops so quickly. One theory is that the planet’s atmosphere’s freezing temperatures and fluid gas flow reduce friction to the point where it’s possible to generate fast-moving winds.
6. Neptune in the Solar System’s Coldest Planet: Temperatures on Neptune can reach 51.7 Kelvin, or -221.45 degrees Celsius (-366.6 degrees Fahrenheit), at the top of its clouds. That’s nearly three times the coldest temperature ever recorded on Earth (-89.2°C; -129°F), implying that an unprotected human would freeze in a split second! Pluto’s temperature drops to 33 K (-240 °C/-400 °F) as it grows colder. Pluto, on the other hand, is no longer a planet (remember?)
7. There are Rings on Neptune: Saturn is usually the planet that springs to mind when people think of ring systems. Would it surprise you to learn that Neptune, too, has a ring system? Unfortunately, it is more difficult to see than Saturn’s bright, bold ring, which is why it isn’t as well-known. Neptune has five rings in all, each named after an astronomer who made significant discoveries concerning the planet — Galle, Le Verrier, Lassell, Arago, and Adams.
These rings are made up of at least 20% dust particles (with some containing up to 70%) that are micrometer-sized, similar to the particles that make up Jupiter’s rings. Small rocks make up the rest of the ring’s ingredients. Because the planet’s rings are dark, it’s difficult to notice them. This is likely owing to the presence of organic compounds that have been changed by cosmic radiation. This is similar to Uranus’ rings, but it is considerably different from Saturn’s icy rings.
The rings of Neptune are thought to be quite young, significantly younger than the Solar System’s age, and much younger than Uranus’ rings. They are thought to be the result of a collision between several of Neptune’s primordial moons, which is consistent with the notion that Triton was a Kuiper Belt Object (KBO) that was grabbed by Neptune’s gravity.
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8. Neptune’s Largest Moon, Triton, was most likely captured: Triton, Neptune’s largest moon, orbits the planet in a retrograde orbit. That is, in comparison to Neptune’s other moons, it orbits the planet backward. This is interpreted as evidence that Neptune grabbed Triton, as the moon did not develop in the same way as the rest of Neptune’s moons. Triton is drifting inward towards Neptune, bound in a synchronized rotation with the planet.
Triton will most certainly be broken apart by Neptune’s gravitational forces and become a spectacular ring around the planet billions of years from now. This ring will be drawn inward and collide with the planet. It’s really unfortunate that such an event won’t happen for a long time, because it would be incredible to witness!
9. Only Once Has Neptune Been Seen Up Close: The only spacecraft to visit Neptune was NASA’s Voyager 2 spacecraft, which did so as part of its Grand Tour of the Solar System. On August 25, 1989, Voyager 2 flew by Neptune, passing within 3,000 kilometers of the planet’s north pole. This was Voyager 2’s closest approach to any object since it was launched from Earth.
Voyager 2 explored Neptune’s atmosphere, rings, and magnetosphere during its approach, as well as conducted a close flyby of Triton. According to Hubble Space Telescope studies, Voyager 2 apparently saw Neptune’s “Great Dark Spot,” a spinning storm system that has since vanished. The information obtained by Voyager helped to shed light on the true nature of this phenomenon, which was previously assumed to be a massive cloud.
10. There Are No Plans to Return to Neptune: The incredible photos of Neptune taken by Voyager 2 may be the last we see for decades, as there are no solid plans to return to the Neptune system. NASA, on the other hand, has suggested that a Flagship Mission could take place in the late 2020s or early 2030s. In 2003, for example, NASA revealed tentative plans to deploy the Neptune Orbiter, a new Cassini-Huygens-style mission to Neptune.
This spacecraft, also known as a “Neptune Orbiter with Probes,” was scheduled to launch in 2016 and would get near Neptune by 2030. The projected expedition would examine the planet’s weather, magnetosphere, ring system, and moons from orbit. However, there has been no news about this project in recent years, and it looks to have been abandoned.