The History Of Neptune

As the last known gas planet, the planet Neptune received its name from the Roman “god of the Sea.” However, the Greek equivalent for Neptune is called “Poseidon.” Since the planet cannot be seen with a simple telescope, it was discovered by observing the effects of its gravitational pull on Uranus.

As the eighth planet in the solar system, the first astronomer to calculate the position of Neptune is Englishman, John C. Adams. After careful calculation of the location of the planet, Adams sent data to the Astronomer Royal of England in 1845. However, astronomers during this time ignored his calculations. In 1846, Urbain J.J. Le Verrier carried out similar calculations, and sent his findings to Johann G. Galle from the Berlin Observatory, who was able to pinpoint the direct location of Neptune.

The Orbit Of Neptune

The orbit of Neptune around then Sun takes approximately 165 Earth years. This orbit is oval in shape, with its perihelion being 2.77 billion miles (4.46 billion km), and its aphelion 2.82 billion miles (4.54 billion km) from the Sun.

It has an average distance of 2.8 billion miles (4.5 billion km) from the Sun. A day on Neptune lasts approximately 16 hours and 7 minutes, and the planet is tilted 28 degrees on its axis.

Expeditions To Neptune

There has only been one expedition to Neptune by the Voyager 2 spacecraft. This expedition was successful in transmitting information about six of the moons of Neptune, along with the discovery of a ring system around the planet.

The Voyager 2 expedition was also noteworthy in measuring the diameter of Neptune, and documenting its magnetic field. Earth received the photos of the expedition to Neptune in 1989.

Exploring A Day On Neptune

A day on Neptune would last 16 hours and 7 minutes, because it is a gas planet. It has a diameter of 30,775 miles, and like the other gas planets, it is composed of hydrogen and helium. Neptune is also composed of lesser amounts of water, methane, and silicates. The highest concentration of gases in the atmosphere is hydrogen.

The temperature of Neptune is an average of -313 degrees Fahrenheit, but it is not the coldest planet in the Solar System. Due to a tilt on its axis, Neptune has noticeable seasons.

There is a thick cloud cover, which surrounds the surface of Neptune. This thick cover has clouds, which move at 700 miles per hour. The blue clouds, which are found at the boundaries of Neptune’s atmosphere, are composed of frozen methane. Closer to the “surface” of Neptune are darker clouds, which astronomers believe contain hydrogen sulfide.

The speeds at which these clouds move show that Neptune does have a large, active wind system. This active wind system is evident in the Great Dark Spot (GDS) of Neptune. The twirling hurricane-like winds of the Great Dark Spot were first seen in 1989 by Voyager 2. However, when the Hubble Telescope viewed Neptune in 1994, the Great Dark Spot had disappeared. The Great Dark Spot was measured to be the same diameter of planet Earth.

Like the other gas planets of its kind, Neptune does not have a solid surface. At the core of the planet is believed to be molten rock, along with frozen methane and ammonia, with a liquid layer of hydrogen and helium surrounding it. The liquid layer then changes to a layer of compressed gas of mainly hydrogen and helium.

The ring system of Neptune consists of five named rings - two quite visible rings, and three lighter rings. The main rings of Neptune are named after the astronomers who made discoveries about the planet. The outermost ring of Neptune is named Adams at 62,930 km from Neptune, followed by Arago, Lassell, Le Verrier, and Galle at 41,900 km from Neptune. It is believed that like the rings of Neptune consist of dust and debris. 

The outermost ring Adams, also possess a series of ring arcs, which represent rings that have not fully formed. The rings arcs are called Fraternité, Courage, Liberté, Egalité 1, and Egalité 2. The longest ring arc is approximately 6,000 miles in length, while the shortest ring arc is approximately 600 miles in length.

Only a little is known about this planet, and no life form has been found on Neptune.   

The Satellites Of Neptune

There are 13 natural satellites associated with Neptune. The main satellites are called Triton, Nereid, and Proteus.

Triton

As a natural satellite of Neptune, Triton (Neptune I) is well known as a large satellite, which rotates around Neptune in retrograde fashion. It is also the only known satellite in the Solar System to orbit a planet in this way. It is sphere-shaped with a surface consisting of water ice and rocky material, with a large portion of its surface being more rocky material than water ice. Another interesting feature on the surface of Triton are the active volcanoes and geysers. These volcanoes and geysers release varying amounts of liquid nitrogen or methane gas into the atmosphere. There are also craters present on the surface of Triton revealing numerous impact collisions involving this satellite. 

This satellite was named after the son of Neptune. It was discovered on October 10, 1846.  Triton has a diameter of 1,352 km, and is located 354,800 km from Neptune. It orbits Neptune every –5.8 Earth days.

Nereid

This is the second satellite of Neptune. It has an eccentric orbit, which varies from 1.3 million kilometers to 9.6 million kilometers. No other known satellite exhibits such a more irregular orbit than Nereid. Nereid reflects twelve percent of the sunlight reaching it. It orbits Neptune every 360 Earth days. Nereid was discovered by Gerard Kuiper in 1949, and has a diameter 340 km.

Proteus

Proteus is the eighth moon of Neptune and the darkest of all of Neptune’s satellites. The surface of Proteus is very similar to the surface of Earth’s moon. It is cold, heavily cratered, and consists of rocky material. It was discovered by Voyager 2 in 1989. Proteus orbits Neptune once every Earth day. 

The full list of Neptune’s satellites and their year of discovery appear below:

Table 1: Concise statistics on the planet Jupiter (N.A.S.A. 2006)

Statistics About Neptune

Discovered By	Johann Galle
Date of Discovery	1846
Average Distance from the Sun	Metric: 4,498,252,900 km English: 2,795,084,800 miles Scientific Notation: 4.4982529 x 109 km (30.069 A.U.) By Comparison: 30.069 x Earth
Perihelion (closest)	Metric: 4,459,630,000 km English: 2,771,087,000 miles Scientific Notation: 4.45963 x 109 km (29.811 A.U.) By Comparison: 29.820 x Earth
Aphelion (farthest)	Metric: 4,536,870,000 km English: 2,819,080,000 miles Scientific Notation: 4.53687 x 109 km (30.327 A.U.) By Comparison: 30.326 x Earth
Equatorial Radius	Metric: 24,764 km English: 15,388 miles Scientific Notation: 2.4764 x 105 km By Comparison: 3.883 x Earth
Equatorial Circumference	Metric: 155,597 km English: 96,683 miles Scientific Notation: 1.55597 x 105 km
Volume	Metric: 62,526,000,000,000 km3 Scientific Notation: 6.2526 x 1013 km3 By Comparison: 57.7 x Earth's
Mass	Metric: 102,440,000,000,000,000,000,000,000 kg Scientific Notation: 1.0244 x 1026 kg By Comparison: 17.147 x Earth's
Density	Metric: 1.76 g/cm3 By Comparison: 0.317 x Earth
Surface Area	Metric: 7,640,800,000 km2 English: 2,950,100,000 square miles Scientific Notation: 7.6408 x 109 km2 By Comparison: 14.980 x Earth
Equatorial Surface Gravity	Metric: 10.71 m/s2 English: 35.14 ft/s2 By Comparison: If you weigh 100 pounds on Earth, you would weigh 110 pounds on Neptune.
Escape Velocity	Metric: 85,356 km/h English: 53,038 mph Scientific Notation: 23,710 m/s By Comparison: Escape velocity of Earth is 25,022 mph.
Sidereal Rotation Period (Length of Day)	0.67125 Earth days 16.11 hours By Comparison: 0.673 x Earth
Sidereal Orbit Period (Length of Year)	164.79 Earth years 60,190 Earth days
Mean Orbit Velocity	Metric: 19,720 km/h English: 12,253 mph Scientific Notation: 5,477.8 m/s By Comparison: 0.490 x Earth
Orbital Eccentricity	.00859 By Comparison: 0.514 x Earth
Orbital Inclination to Ecliptic	1.769 degrees
Equatorial Inclination to Orbit	29.58 degrees By Comparison: 1.261 x Earth
Orbital Circumference	Metric: 28,142,000,000 km English: 17,487,000,000 miles Scientific Notation: 2.8142 x 1010 km By Comparison: 30.44 x Earth
Effective Temperature	Metric: -214 °C English: -353 °F Scientific Notation: 59 K
Atmospheric Constituents	Hydrogen, Helium, Methane Scientific Notation: H2, He, CH4 By Comparison: Earth's atmosphere consists mostly of N2 and O2.
Table 2: Concise statistics on the planet Neptune (N.A.S.A. 2006)

References

Encyclopedia Britannica. “Neptune.” 2006. Encyclopedia Britannica Premium Service. 2006 http://www.britannica.com/eb/article-54304

Smith, Bradford A. "Neptune." World Book Online Reference Center. 2004. World Book, Inc. http://www.worldbookonline.com/wb/
Article?id=ar386900

National Aeronautics and Space Administration (N.A.S.A).“Neptune: Facts & Figures” 2006.
http://solarsystem.nasa.gov/planets/profile.cfm?Object=
Neptune&Display=Facts

Solar Views. “Neptune.” 2001 http://www.solarviews.com/eng/neptune.htm

Space Today Online. “Exploring The Neptune System.” 2004.
http://www.spacetoday.org/SolSys/Neptune/NeptuneMoons.html

Neptune Images