Many people equate Neptune with Spongebob Squarepants or The Little Mermaid, and while they are great that isn’t the Neptune we mean here. Neptune is the furthest planet from the sun and was thought to be a star for a time.
Neptune is one of our favourite planets, and we present you with 10 facts about Neptune that you may not be aware of.
1 Neptune was discovered by mathematical calculations
The first person known to have observed Neptune was Galileo Galilei, who noted it as a star in one of his drawings. Because he did not identify it as a planet, he is not solely credited with the planet’s discovery. For over 200 years, Neptune lay hidden inside the network of stars in Galileo’s notes and drawings.
In September 23, 1846, two mathematicians named Frenchman Urbain Le Verrier and British man John Couch Adams predicted that a new planet – then named “Planet X” would be discovered in a specific region of the sky. Astronomer, Johanne Gottfried Galle from Germany used Le Verrier’s calculations to find Neptune.
Did you know?
Interesting historical facts about Neptune: Both Great Britain and France lay claim to the planet’s Discovery. This dispute was amplified by political tensions between Great Britain and France, at the time. Today, all three are credited with Neptune’s discovery.
2 Neptune is the densest gas giant in the solar system
Neptune is approximately 17 times the mass of Earth but is also 4 times larger than Earth; its mass is spread out over a larger volume. The average density of the planet is 1.6 gm/cm3.
This makes Neptune approximately:
- 19% more dense than Jupiter and Uranus. (1.3 gm/cm3)
- 57% more dense than Saturn. (0.7 gm/cm3)
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Gravity on Neptune is the closest to that of Earth. Neptune’s gravity is approximately 17% stronger than Earth’s gravity (one g).
3 Neptune is the farthest planet from the sun
Neptune was classed as the most distant planet in the solar system up until 1930 when Pluto was discovered. Neptune then became the 2nd most distant planet in the solar system. In 2006, Pluto was reclassified as a dwarf planet and Neptune secured its original title again.
Did you know?
Between 1979 and 1999, Pluto’s elliptical, egg-shaped orbit brought Pluto closer to the sun than Neptune. For those 20 years, the title of the most distant planet was incorrect.
4 Only one spacecraft has visited Neptune
Voyager 2 flew by the planet on August 25, 1989, and remains the only spacecraft to visit Neptune. It remains in operation today and has up to now been operating for over 43 years (as of the 2nd of December, 2023).
Did you know?
There have been two cancelled space missions to Neptune: Neptune Orbiter, in 2016, and Argo in 2019. The next mission concept is Odinus which is planned to launch in 2034.
5 Chilly facts about Neptune: it is the coldest planet in the solar system
Temperatures on Neptune can reach -221.45 °C which is almost 3 times colder than the coldest temperatures ever recorded on Earth at -89.2°C.
Did you know?
Neptune became the coldest planet in the solar system when Pluto was reclassified as a dwarf planet in 2006.
6 Did you know these facts about Neptune: it is the smallest of the gas giants
Neptune is the smallest of the 4 gas giants in terms of diameter, however, takes the third place ahead of Uranus in terms of Mass and is 17 times as massive as Earth.
Did you know?
Although Neptune is the smallest of the Gas Giants, the average diameter across the planet is 4 times the diameter of Earth; that’s a lot of gas!
7 Neptune’s winds are the fastest in the solar system
Winds on Neptune can reach up to 1,500 mph (2,414 kmh). Neptune’s most famous storm named the Great Dark Spot was first observed in 1982 by the Voyager 2 spacecraft. It was approximately the size of Earth and reached 1,500 mph.
Five years later the Hubble Space Telescope found that yet another smaller storm had appeared in the northern hemisphere. This storm was the size of Earth’s moon and was named the Small Dark Spot.
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Winds on Neptune are up to 4.71 times stronger than Earth’s most damaging tornados. A tornado on Earth is measured by the Fujita (not, the Fajita) scale. Tornadoes are measured on a scale of F0-5, with F5 being an “Incredible Tornado.” F5 tornados reach between 261 and 318 Mph.
8 Neptune has 5 main rings
Neptune has five faint main rings. The three main rings are named after the three people who discovered Neptune. The Adams ring, the Le Verrier ring and the Galle ring.
The also has 4 ring arcs. These have gaps and do not constitute a full ring. These are named Courage, Liberté, Egalité 1, Egalité 2 and Fraternité (Courage, Liberty, Equality and Fraternity).
Did you know?
Astronomers once believed that the matter within the ring arcs would spread out over time. They now believe that the arcs are controlled by the gravitational effects of Neptune’s moon, Galatea.
More recent Earth-based observations have shown that the ring arcs may decay and predict that the Liberté arc may disappear in around 100 years.
9 Neptune is named after the Roman god of the sea
In Roman mythology, Neptune was the god of the sea. In ancient Greek, it is identified with Poseidon. Modern Greeks still call the planet Poseidon to this day.
Did you know?
Neptune has had many names. Originally, when it was theorised to exist, it was labelled as “planet x”. After it was discovered, each of the astronomers simply called it “the planet exterior to Uranus” among suggested names.
These other suggested names included Oceanus, Janus and Neptune. By December 29, 1846, more astronomers and nations became involved. Soon after this, Neptune became the accepted name.
10 The last of our facts about Neptune: the planet has 14 moons
Neptune currently has 14 discovered moons. Triton is the largest of these and the only one that is spherical. Scientists believe that Triton was in fact a dwarf planet that was captured by the gravity of Neptune. It is the only moon in the solar system that orbits in the opposite direction to its planet, and it is also the coldest known object in the solar system.
Did you know?
Neptune’s known moons are named after sea gods and nymphs in Greek mythology. They are: Triton, Thalassa, Naiad, Nereid, Proteus, Neso, Despina, Hippocamp, Galata, Halimede, Psamathe, Laomedeia, Larissa and Sao.
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