Facts about Neptune

Neptune

Neptune is the eighth planet in the solar system and named after Roman god of the sea. It has the fourth-largest planetary diameter and third-largest planetary mass in the Solar System. In 2006, Neptune becomes the most distant planet in the solar system after the demotion of Pluto as a dwarf planet. The planet orbit the sun at an average distance of 4.5 billion km, which is equal to 30 times the distance of the Earth from the Sun. Neptune's gravity is slightly stronger than Earth's. A 100-pound person on earth would weight 114-pounds on Neptune. Like its neighbour Uranus, it has probably a rocky core surrounded by a thick mantle of icy materials (water, ammonia and methane). Check out these interesting facts about the most distant planet Neptune.

Planet Profile

Name	Neptune
Knowm Satellite	14
Distance from Sun (avg)	4.495 billion km
Equatorial Radius	24,764 km
Polar Radius	24,341 km
Volume	6.254 × 10¹³ km³
Mass	1.024 × 10²⁶ kg
Surface area	7.618 billion km²
Gravity	11.15 m/s²
Surface Temperature ( at 1 bar)	-201 ℃ or -329 °F
Length of day	0 day 16 hrs 6 min (earth time)
Length of year	165 Earth years
Astronomical symbol	♆

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Quick Facts About Neptune

Neptune is the only planet to have been discovered using mathematical calculations.
All the moons of Neptune are named after Greek and Roman water gods.
The first and only spacecraft to visit Neptune was NASA's Voyager 2 in 1989.
The signal from Voyager 2 takes 246 days 4 hrs and 6 min to reach back to the Earth.
It is so far that light from the sun takes about 4 hrs and 10 min to reach Neptune.
Neptune has the third strongest gravity in the solar system, only after Sun and Jupiter.
Like other gas giants, Neptune has also rings.
Some part of the rings are brighter than others and appear as arcs.
The magnetic field of Neptune is 27 times stronger than Earth's.
Unlike other planets, whose magnetic field aligns with their axis, Neptune's magnetic field is tilted 47 ° from the planet's axis.

Detailed Facts about Neptune

Neptune was mathematically predicted before its direct observation

Urbain Le Verrier (left) and John Couch Adams (right)

Alexis Bouvard was a 19th-century French astronomer, who while observing Uranus, find some irregularities in its orbit. The planet's position was not as it was mathematically predicted to be. He finally deduced it was because of the gravity of a nearby unseen world. Two mathematicians, John Couch Adams in England and Le Verrier in France took this data and began to work independently from one another. Both predicted that a new planet would be discovered in a specific region in the sky.

On the evening of September 23, 1846, three years after Bouvard's death, Johann Gottfried Galle of Germany became the first man to actually see the distant world. At the urging of Le Verrier and with some help from Observatory student Heinrich. The rest, Galley was able to pinpoint the cause of Bouvard's deviations in Uranus's orbit. In 1846, the international astronomy community credited both Le Verrier and Adams as the discoverer of Neptune.

Neptune was named after the Roman God of sea and freshwater

Neptune - Roman god of sea
© Wikimedia

Known to the Greeks as Poseidon, Neptune was the brother of Jupiter - god of thunder and uncle of Minerva - goddess of wisdom. He was both, worshipped and feared by ancient sailors. Who relied on Neptune's goodwill to guide them safely on long and often dangerous voyages. Romans dedicated a July feast to the sea god complete with games and sacrifices.

After its discovery, Neptune was introduced as "the planet exterior to Uranus" and "Le Verrier's planet". Galle was the first to suggest a proper name for the planet. He put the name "Janus". In England, Challis, the director of Cambridge Observatory suggested the name "Oceanus". While Le Verrier wanted to name it as "Le Verrier" because he discovered it. Even he falsely claimed that his idea has been approved by the French Bureau. It was Friedrich Georg, a German astronomer who proposed the name "Neptune" in 1846.

Neptune is the smallest of the gas giants but still several times larger than Earth

Neptune compared to Earth

The volume of Neptune is 6.25 x 1013 km3. In simpler terms, it is about 58 times the Earth's volume. Which means, it could fit 58 Earths inside it. In terms of mass, it is about 1.02 x 1026 kg or 102 trillion kg. Which make it the third most massive planet in the solar system. By diameter, it is the fourth-largest planet, which is about 49,200 km. Making it a whopping four times that of Earth's diameter.

The equatorial circumference of Neptune measures around 96,685 miles or 155,600 kilometres. By comparison, Earth's circumference stretches just 25,000 miles or 40,000 kilometres. A road trip across Neptune's equator would have done at a steady pace of 60 mph or 96 km/h would take approximately 1600 hours or 67 days to cross.

Neptune is mainly made up of icy material

Interiors of gas giant

Scientists calculate that Neptune is made up of 60 to 70 per cent icy material - water, ammonia and methane. Due to icy composition, Neptune is often referred to as "ice giant". The atmosphere is mainly composed of hydrogen and helium with a trace amount of methane. So, with all that ice, it is no wonder that Neptune gets its icy blue hue, right. Well not quite! The planet gets its distinct colour from little bit methane in its atmosphere. Which absorbs red light and acts as a reflector for blue wavelengths.

However, its neighbour Uranus is much lighter in colour which has even more methane than Neptune, about 2.5% compared to 1.5%. So, this suggests that there is another unknown component that gives Neptune its bright blue colour. Despite its colour, the planet experienced large dark spots or storms that have appeared and vanished from sight.

Neptune is the windiest place in the solar system

It's hard enough for Earthlings to deal with 150 miles or 240 kilometres per hour hurricane winds. But those don't compare to the winds that Neptune routinely dishes out. If you look at the planet, you could see the clouds are changing its position. But most of the change in position is due to the rotation of the planet. If you know the rotation rate and subtract that out, it gives the actual motion of the clouds relative to the planet. That is the real wind speed.

Researchers found that the Neptune's winds are so fast. That they frequently break the sound barrier, hitting speeds of up to 1500 miles or 2,400 kilometres per hour. The energy for making this whether coming from Neptune itself. It does receive sunlight but Neptune radiates away a lot more energy, about 2.6 times that it gets. Which means it has an internal source of heat that drives the fastest wind in the solar system.

There are currently 14 moons orbiting the planet

Neptune's moons and their orbits

Neptune has 14 official moons. Triton is the largest and best-known of the moons, discovered less than three weeks after Neptune was first spotted. It's well known for its retrograde orbit (direction opposite to planet's rotation) and cryovolcanic activity. Meaning that instead of erupting molten rock Triton's volcanoes erupt water and ammonia. In order of discovery Neptune's moons are:

Triton - 1846

Nereid - 1949

Larissa - 1981

Naiad - 1989

Thalassa - 1989

Despina - 1989

Galatea - 1989

Proteus - 1989

Halimede - 2002

Sao - 2002

Laomedeia - 2002

Neso - 2002

Psamathe - 2002

Hippocamp - 2013

While fourteen moons is a lot in earth terms. It isn't much when you compare it to some of our other worlds nearby. For example, Uranus has more than double that number while Jupiter takes the top spot with a whopping 79 moons.

Neptune is the most distant planet in the solar system

Distance of Neptune and other planets from Sun

Since Pluto's demotion from a planet to a dwarf one in 2006, Neptune is now classified as the most distant world in our solar system. As distant it is, Neptune's orbit is around 2.8 billion miles or 4.5 billion kilometres away from the Sun. To simplify this massive number just imagine being 30 times farther away from the Sun as you are on earth.

As it follows an elliptical orbit like other planets, this number varies throughout the years. When it is closest to the sun (perihelion), it is at a distance of about 4.46 billion km or 2.77 billion miles. At its farthest point (aphelion), it is around 4.54 billion km or 2.82 billion miles. It is no wonder that Voyager 2, the only spacecraft to observe Neptune up-close, took 12 years to reach the icy planet. Despite travelling at a speed of over 35,000 miles or 56,000 kilometres per hour.

Since its discovery, Neptune has only completed one orbit

Orbits of Neptune and other outer planets with their positions

Neptune's day cycles are much shorter than Earth's, totalling about 16 hours long. In fact, Neptune has the third shortest day of any planet in our solar system. Only getting beaten out by Jupiter and Saturn which both have around a 10-hour day. The days may be short but the years are extremely long.

It takes Neptune 165 earth years to complete its orbit around the Sun. A Neptunian year is much longer than any other planet. In fact, it was only in 2011 that the planet completed its first orbit since Johann Galle landmark observation. Due to Pluto's unusual orbit, sometimes it is closer to Sun than Neptune. However, Pluto is classified as a dwarf planet, Neptune remains the farthest planet in the solar system.

Neptune has also rings but they are much fainter than other gas giants

Neptune's full rings image taken by Voyager 2

Scientist recently confirmed that Neptune like Saturn and Uranus has a total of six very faint rings. In fact, the existence of the Rings were visually confirmed in 1989. Though, their existence was discovered in 1984. Neptune's rings have only about a thousandth the total mass of Uranus's.

Despite covering a space of 77,500 miles or 125,000 kilometres the Rings are so faint. That a passing astronaut would be unable to see them with the naked eye. Instead at most, he would see a few bright arcs representing Neptune's outer narrow ring. Don't expect to see those rings for long they've been steadily deteriorating. With at least one expected to vanish by this next century.

Neptune is a very cold and very hot place

Neptune's atmosphere is colder than anything seen on our planet. With temperatures plummeting as low as - 210 ℃ or - 346 °F. To put that into perspective, the coldest recorded temperature on earth was just -89 ℃ or minus 127 °F in East Antarctica. Despite its cold temperature and distance from the Sun, it is not the coldest place in the solar system. That credit goes to seventh planet Uranus that has an average temperature of −224.2 °C; −371.5 °F.

Now with that, Neptune has an extremely hot core that produces temperatures hotter than the surface of our Sun, about 7,000 ℃ or 12,600 °F. Neptune's core is so hot that it generates most of the planet's heat as opposed to relying on the Sun upon. So Neptune is an icy planet filled with Sun scorching warmth.

Neptune experiences huge disappearing storms

Neptune's Great Dark Spot

When NASA's Voyager 2 visited Neptune in 1989, it discovered two immense dark storms turning through Neptune's thick blue atmosphere. The larger of them was called the Great Dark Spot which was the size of our Earth. Jupiter's Great Red Spot has existed for hundreds of years but when Hubble looked at Neptune in 1994, the Great Dark Spot was already gone. Instead in 2016, there was a new storm on the northern hemisphere which was named as the Northern Great Dark Spot.

It is unknown to us whether this storm still exists on Neptune because Hubble observations are limited. A program has begun called the Outer Planet Atmospheres Legacy or OPAL to gather global maps of our gas giant planets every year. We really don't know why large storms on Neptune form and dissipate much more rapidly than storms on Jupiter.

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