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Neptune planet is the eighth and farthest known planet at a distance of 4.5 billion km (30.1 AU) from the sun in the solar system.

Image1: neptune planet

It is 17 times massive the earth and holds the tag of fourth largest planet by diameter and third most massive planet in the solar system. Neptune is the only planet in the solar system found by mathematical prediction. It is an ice giant, made of mostly dense fluid of icy materials like water, methane, and ammonia above a small rocky core.

Day and Year

Neptune takes about 165 earth years to complete the orbit around the sun and 17 hours to rotate on its own axis.

Because Neptune is not a solid body, its atmosphere undergoes differential motion. The wide equatorial zone rotates with a period of about 18 hours and the polar region rotates with a period of about 12 hours.

The Axial tilt of Neptune is 28.32oC, which is similar to Earth and Saturn. As a result, Neptune experiences similar seasonal changes to Earth. But the long orbital period of Neptune means that the seasons last for forty Earth years.

Surface and Structure

Neptune Structure
Image2: Neptune Structure

Neptune has no solid surface. It is made mostly from helium and Hydrogen. Its atmosphere forms about 5% to 10% of its mass and extends perhaps 10% to 20% of the way towards the core, where it reaches pressures of about 10Gpa. Neptune’s surface gravity (11.15 m/s2) is slightly more than the earth.

The core of Neptune planet, about 1.2 times massive than earth is likely composed of Iron, Nickel, and silicate. The pressure at the center is about 7 Mbar and the temp may be about 5,400 k. Above the core; Hot, dense fluid of Icy material (Water, ammonia, and Methane) exits. This is the region is 10 to 15 times massive than the earth. The scientist also believes that the top of the mantle may be an ocean of liquid carbon with floating solid ‘diamonds’.

Size and Distance

Neptune earth size comparison
Image3:Size comparison of the Neptune and the Earth

The mean radius of neptune is 24622 km; 4 times wider than is 17.147 times massive than earth with a mass of 1.024×1026 kg.

From an average distance of 2.8 billion miles (4.5 billion km), Neptune is 30 AU away from the Sun. From this distance, it takes Sunlight 4 hours to travel from the Sun to Neptune.

Distance and size Between sun And neptune
Image4: Distance and size Between sun And neptune


Its atmosphere is made up mostly of 80% molecular hydrogen, 19% atomic helium, and trace amount methane. Atmospheric methane absorbs the red light, which gives Neptune blue colour. Some unknown atmospheric constituent is thought to contribute to Neptune’s colour.

Neptune cloud
Image5: Bands of high-altitude clouds cast shadows on Neptune’s lower cloud deck
neptune great dark spot
Image6: The Great Dark Spot, as imaged by Voyager 2

Neptune’s atmosphere is sub divided into two main regions: the lower troposphere, where temp decreases with altitude, and the stratosphere, where temp increases with altitude.

On the southern hemisphere of Neptune, there is a great dark spot like a great red spot on Jupiter. These weather patterns are driven by the sustained winds of any planet in the solar system, with recorded wind speed as high as 2100km/h.

Orbital and escape velocity

Neptune average orbital speed is 5.43 km/s and escape velocity is 23.5 km/s.


Neptune’s magnetic field is tilted 47o relative to the rotational axis and offset 0.55 radii (13,500 km) from the planet’s physical center.

The magnetopause (pressure of the magnetosphere counterbalances the solar wind) lies at a distance of 23–26.5 times the radius of Neptune. The tail of the magnetosphere extends out to at least 72 times the radius of Neptune, and likely much farther.

The magnetic field of Neptune is 27 times stronger than the Earth.


Image7: Natural-colour view of Neptune with Proteus, Larissa , and Despina, from the Hubble Space telescope

Neptune has 14 know moons (Proteus, Larissa, Despina, Triton, Nereid, naiad, Thalassa, Despina, Galatea, etc.). Triton is the largest Neptunian moon, comprising more than 99.5% of the mass in orbit around Neptune and it is the one planet’s moon in the solar system that circles its planet in the opposite direction to the planet rotation (a retrograde orbit).

The second discovered Neptune’s moon; Nereid has one of the most eccentric orbits of any satellite in the Solar System. Naiad, Thalassa, Despina, and Galatea are the Neptune’s innermost moons, orbit close enough to be within Neptune’s ring.


neptune's ring
Image8: The Neptune’s Ring

Neptune has at least five main rings and four more ring arcs. The rings may consist of ice particles coated with silicates or carbon based materials, which most likely gives them a reddish color.

The five main rings are the narrow Adams Ring, 63,000 km from the center of Neptune, the Le Verrier Ring, at 53,000 km, and the broader, fainter Galle Ring, at 42,000 km. A faint outward extension to the Le Verrier Ring has been named Lassell; it is bounded at its outer edge by the Arago Ring at 57,000 km.

The outermost ring, Adams, contains five prominent arcs now named Courage, Liberty, Egality 1, Egalite2, and Fraternity. The arcs are strange because the laws of motion would predict that arcs would spread out into a uniform ring over short timescales. Now scientists estimate that the arcs are corralled into their current form by the gravitational effects of Galatea, a moon just inward from the ring.


Neptune does not support life. The temp & pressure, and materials of the planet too extreme and volatile to adopt life.

Human Touch

Voyager 2 is the only and first spacecraft that has visited Neptune. The spacecraft’s closest approach to the planet occurred on 25 August 1989 passing about 4,800 km (2,983 miles) above the planet’s North Pole. The spacecraft verified the existence of a magnetic field surrounding the planet and discovered that the field was offset from the center and tilted in a manner similar to the field around Uranus. They also discovered six new moons and the shown planet have more than one ring. There have been discussions to launch Neptune missions sooner. In 2003, there was a proposal in NASA’s “Vision Missions Studies” for a Neptune Orbiter with Probes.


In Roman religion, Neptune is the god of free water and the sea. He was worshipped by the Romans also as a god of horses, under the name NeptunusEquester, a patron of horse racing.

Neptune is the son of Saturn and Ops and father of Triton, Proteus, Rhodes, and Benthesikyme. Neptune is the brother of Jupiter and Pluto the brothers presided over the realms of Heaven, the earthly world, and the underworld Salacia is his wife.

In Hindu religion Neptune is known as Varuna; the god of the ocean. His vehicle is Makara (Crocodile) and his weapon is a Pasha (noose, rope loop). Varuna is the son of kashyapa and Aditi and his consort is Varuni.

Quick Discover :

Planet Type:

Ice gaint

Distance from the sun:

30.1 Astronomical unit


24622 KM

Escape velocity:

23.5 km/s

Average orbital speed:

5.43 km/s

Equatorial rotational velocity:

9650 km/h

Earth Year:

165 Earth Years

Earth Day:

16 hours.

Axial tilt:


Surface gravity:

11.15 m/s2

Mean density:

1.64 g/cm3


1.024×1026 Kg





Potential for Life:

No life

Image credit :



Image4: universediscover/aniketkumar






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