The Planet Neptune - Universe Today Universe Today by Matt Williams Neptune is the eight planet from our Sun, one of the four gas giants, and one of the four outer planets in our Solar System. Since the “demotion” of Pluto by the IAU to the status of a dwarf planet – and/or Plutoid and Kuiper Belt Object (KBO) – Neptune is now considered to be the farthest planet in our Solar System. As one of the planets that cannot be seen with the naked eye, Neptune was not discovered until relatively recently. And given its distance, it has only been observed up close on one occasion – in 1989 by the Voyager 2 spaceprobe. Nevertheless, what we’ve come to know about this gas (and ice) giant in that time has taught us much about the outer Solar System and the history of its formation. Discovery and Naming: Neptune’s discovery did not take place until the 19th century, though there are indications that it was observed before long that.

For instance, Galileo’s drawings from December 28th, 1612, and January 27th, 1613, contained plotted points which are now known to match up with the positions of Neptune on those dates. However, in both cases, Galileo appeared to have mistaken it for a star. 1821, French astronomer Alexis Bouvard published astronomical tables for the orbit of Uranus. Subsequent observations revealed substantial deviations from the tables, which led Bouvard to hypothesize that an unknown body was perturbing Uranus’ orbit through gravitational interaction. New Berlin Observatory at Linden Street, where Neptune was discovered observationally. Credit: Leibniz-Institute for Astrophysics Potsdam In 1843, English astronomer John Couch Adams began work on the orbit of Uranus using the data he had and produced several different estimates in the following years of the planet’s orbit. In 1845–46, Urbain Le Verrier, independently of Adams, developed his own calculations, which he shared with Johann Gottfried Galle of the Berlin Observatory .

Galle confirmed the presence of a planet at the coordinates specified by Le Verrier on September 23rd, 1846. The announcement of the discovery was met with controversy, as both Le Verrier and Adams claimed responsibility. Eventually, an international consensus emerged that both Le Verrier and Adams jointly deserved credit. However, a re-evaluation by historians in 1998 of the relevant historical documents led to the conclusion that Le Verrier was more directly responsible for the discovery and deserves the greater share of the credit. Claiming the right of discovery, Le Verrier suggested the planet be named after himself, but this met with stiff resistance outside of France. He also suggested the name Neptune, which was gradually accepted by the international community. This was largely because it was consistent with the nomenclature of the other planets, all of which were named after deities from Greco-Roman mythology. Neptune’s Size, Mass and Orbit: With a mean radius of 24,622 ± 19 km, Neptune is the fourth largest planet in the Solar System and four times as large as Earth.

But with a mass of 1.0243×1026 kg – which is roughly 17 times that of Earth – it is the third most massive, outranking Uranus. The planet has a very minor eccentricity of 0.0086, and orbits the Sun at a distance of 29.81 AU (4.459 x 109 km) at perihelion and 30.33 AU (4.537 x 109 km) at aphelion. A size comparison of Neptune and Earth. Credit: NASA Neptune takes 16 h 6 min 36 s (0.6713 days) to complete a single sidereal rotation, and 164.8 Earth years to complete a single orbit around the Sun. This means that a single day lasts 67% as long on Neptune, whereas a year is the equivalent of approximately 60,190 Earth days (or 89,666 Neptunian days).

Because Neptune’s axial tilt (28.32°) is similar to that of Earth (~23°) and Mars (~25°), the planet experiences similar seasonal changes. Combined with its long orbital period, this means that the seasons last for forty Earth years. Also owing to its axial tilt being comparable to Earth’s is the fact that the variation in the length of its day over the course of the year is not any more extreme than it on Earth. Neptune’s orbit also has a profound impact on the region directly beyond it, known as the Kuiper Belt (otherwise known as the “Trans-Neptunian Region”). Much in the same way that Jupiter’s gravity dominates the Asteroid Belt , shaping its structure, so Neptune’s gravity dominates the Kuiper Belt. Over the age of the Solar System, certain regions of the Kuiper belt became destabilised by Neptune’s gravity, creating gaps in the Kuiper belt’s structure. There also exists orbits within these empty regions where objects can survive for the age of the Solar System. These resonances occur when Neptune’s orbital period is a precise fraction of that of the object – meaning they complete a fraction of an orbit for every orbit made by Neptune.

The most heavily populated resonance in the Kuiper belt, with over 200 known objects, is the 2:3 resonance. Objects in this resonance complete 2 orbits for every 3 of Neptune, and are known as plutinos because the largest of the known Kuiper belt objects, Pluto , is among them. Although Pluto crosses Neptune’s orbit regularly, the 2:3 resonance ensures they can never collide. Neptune has a number of known trojan objects occupying both the Sun–Neptune L4 and L5 Lagrangian Points – regions of gravitational stability leading and trailing Neptune in its orbit. Some Neptune trojans are remarkably stable in their orbits, and are likely to have formed alongside Neptune rather than being captured. Neptune’s Composition: Due to its smaller size and higher concentrations of volatiles relative to Jupiter and Saturn, Neptune (much like Uranus) is often referred to as an “ice giant” – a subclass of a giant planet. Also like Uranus, Neptune’s internal structure is differentiated between a rocky core consisting of silicates and metals; a mantle consisting of water, ammonia and methane ices; and an atmosphere consisting of hydrogen, helium and methane gas.

The core of Neptune is composed of iron, nickel and silicates, with an interior model giving it a mass about 1.2 times that of Earth. The pressure at the center is estimated to be 7 Mbar (700 GPa), about twice as high as that at the center of Earth, and with temperatures as high as 5,400 K. At a depth of 7000 km, the conditions may be such that methane decomposes into diamond crystals that rain downwards like hailstones. The mantle is equivalent to 10 – 15 Earth masses and is rich in water, ammonia and methane. This mixture is referred to as icy even though it is a hot, dense fluid, and is sometimes called a “water-ammonia ocean”. Meanwhile, the 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 10 GPa – or about 100,000 times that of Earth’s atmosphere. Composition of Neptune. Image credit: NASA Increasing concentrations of methane, ammonia and water are found in the lower regions of the atmosphere.

Unlike Uranus, Neptune’s composition has a higher volume of ocean, whereas Uranus has a smaller mantle. Neptune’s Atmosphere: At high altitudes, Neptune’s atmosphere is 80% hydrogen and 19% helium, with a trace amount of methane. As with Uranus, this absorption of red light by the atmospheric methane is part of what gives Neptune its blue hue, although Neptune’s is darker and more vivid. Because Neptune’s atmospheric methane content is similar to that of Uranus, some unknown atmospheric constituent is thought to contribute to Neptune’s more intense coloring. Neptune’s atmosphere is subdivided into two main regions: the lower troposphere (where temperature decreases with altitude), and the stratosphere (where temperature increases with altitude). The boundary between the two, the tropopause, lies at a pressure of 0.1 bars (10 kPa). The stratosphere then gives way to the thermosphere at a pressure lower than 10?5 to 10?4 microbars (1 to 10 Pa), which gradually transitions to the exosphere.

Neptune’s spectra suggest that its lower stratosphere is hazy due to condensation of products caused by the interaction of ultraviolet radiation and methane (i.e. photolysis), which produces compounds such as ethane and ethyne. The stratosphere is also home to trace amounts of carbon monoxide and hydrogen cyanide, which are responsible for Neptune’s stratosphere being warmer than that of Uranus. A modified color/contrast image emphasizing Neptune’s atmospheric features, including wind speed. Credit Erich Karkoschka) For reasons that remain obscure, the planet’s thermosphere experiences unusually high temperatures of about 750 K (476.85 °C/890 °F). The planet is too far from the Sun for this heat to be generated by ultraviolet radiation, which means another heating mechanism is involved – which could be the atmosphere’s interaction with ion’s in the planet’s magnetic field, or gravity waves from the planet’s interior that dissipate in the atmosphere. Because Neptune is not a solid body, its atmosphere undergoes differential rotation.

The wide equatorial zone rotates with a period of about 18 hours, which is slower than the 16.1-hour rotation of the planet’s magnetic field. By contrast, the reverse is true for the polar regions where the rotation period is 12 hours. This differential rotation is the most pronounced of any planet in the Solar System, and results in strong latitudinal wind shear and violent storms. The three most impressive were all spotted in 1989 by the Voyager 2 space probe, and then named based on their appearances. The first to be spotted was a massive anticyclonic storm measuring 13,000 x 6,600 km and resembling the Great Red Spot of Jupiter. Known as the Great Dark Spot , this storm was not spotted five later (Nov. 2nd, 1994) when the Hubble Space Telescope looked for it. Instead, a new storm that was very similar in appearance was found in the planet’s northern hemisphere, suggesting that these storms have a shorter life span than Jupiter’s. Reconstruction of Voyager 2 images showing the Great Black spot (top left), Scooter (middle), and the Small Black Spot (lower right).

Credit: NASA/JPL The Scooter is another storm, a white cloud group located farther south than the Great Dark Spot. This nickname first arose during the months leading up to the Voyager 2 encounter in 1989, when the cloud group was observed moving at speeds faster than the Great Dark Spot. The Small Dark Spot , a southern cyclonic storm, was the second-most-intense storm observed during the 1989 encounter. It was initially completely dark; but as Voyager 2 approached the planet, a bright core developed and could be seen in most of the highest-resolution images. Neptune’s Moons: Neptune has 14 known satellites, all but one of which are named after Greek and Roman deities of the sea ( S/2004 N 1 is currently unnamed). These moons are divided into two groups – the regular and irregular moons – based on their orbit and proximity to Neptune. Neptune’s Regular Moons – Naiad , Thalassa , Despina , Galatea , Larissa , S/2004 N 1, and Proteus – are those that are closest to the planet and which follow circular, prograde orbits that lie in the planet’s equatorial plane.

They range in distance from 48,227 km (Naiad) to 117,646 km (Proteus) from Neptune, and all but the outermost two (S/2004 N 1, and Proteus) orbit Neptune slower than its orbital period of 0.6713 days. Based on observational data and assumed densities, these moons range in size and mass from 96 x 60 x 52 km and 1.9 x 1017 kg (Naiad) to 436 x 416 x 402 km and 50.35 x 1017 kg (Proteus). This composite Hubble Space Telescope picture shows the location of a newly discovered moon, designated S/2004 N 1, orbiting the giant planet Neptune, nearly 4.8 billion km (3 billion miles) from Earth. Credit: NASA, ESA, and M. Showalter (SETI Institute). With the exception of Larissa and Proteus (which are largely rounded) all of Neptune’s inner moons are believed to be elongated in shape.

Their spectra also indicates that they are made from water ice contaminated by some very dark material, probably organic compounds. In this respect, the inner Neptunian moons are similar to the inner moons of Uranus. Neptune’s irregular moons consist of the planet’s remaining satellites (including Triton ). They generally follow inclined eccentric and often retrograde orbits far from Neptune. The only exception is Triton, which orbits close to the planet, following a circular orbit, though retrograde and inclined. In order of their distance from the planet, the irregular moons are Triton, Nereid , Halimede, Sao, Laomedeia, Neso and Psamathe – a group that includes both prograde and retrograde objects. With the exception of Triton and Nereid, Neptune’s irregular moons are similar to those of other giant planets and are believed to have been gravitationally captured by Neptune. In terms of size and mass, the irregular moons are relatively consistent, ranging from approximately 40 km in diameter and 4 x 1016 kg in mass (Psamathe) to 62 km and 16 x 1016 kg for Halimede.

Triton and Nereid are unusual irregular satellites and are thus treated separately from the other five irregular Neptunian moons. Between these two and the other irregular moons, four major differences have been noted. First of all, they are the largest two known irregular moons in the Solar System. Triton itself is almost an order of magnitude larger than all other known irregular moons and comprises more than 99.5% of all the mass known to orbit Neptune (including the planet’s rings and thirteen other known moons). Global Color Mosaic of Triton, taken by Voyager 2 in 1989. Credit: NASA/JPL/USGS Secondly, they both have atypically small semi-major axes, with Triton’s being over an order of magnitude smaller than those of all other known irregular moons. Thirdly, they both have unusual orbital eccentricities: Nereid has one of the most eccentric orbits of any known irregular satellite, and Triton’s orbit is a nearly perfect circle.

Finally, Nereid also has the lowest inclination of any known irregular satellite With a mean diameter of around 2700 km and a mass of 214080 ± 520 x 1017 kg, Triton is the largest of Neptune’s moons, and the only one large enough to achieve hydrostatic equilibrium (i.e. is spherical in shape). At a distance of 354,759 km from Neptune, it also sits between the planet’s inner and outer moons. Triton follows a retrograde and quasi-circular orbit, and is composed largely of nitrogen, methane, carbon dioxide and water ices. With a geometric albedo of more than 70% and a Bond albedo as high as 90%, it is also one of the brightest objects in the Solar System. The surface has a reddish tint, owning to the interaction of ultraviolet radiation and methane, causing tholins . Triton is also one of the coldest moons in the Solar System, with surface temperature of about 38 K (-235.2 °C).

However, owing to the moon being geologically active (which results in cryovolcanism ) and surface temperature variations that cause sublimation, Triton is one of only two moons in the Solar System that has a substantial atmosphere. Much like it’s surface, this atmosphere is composed primarily of nitrogen with small amounts of methane and carbon monoxide, and with an estimated pressure of about 14 nanobar. Triton has a relatively high density of about 2 g/cm3 indicating that rocks constitute about two thirds of its mass, and ices (mainly water ice) the remaining one third. There also may be a layer of liquid water deep inside Triton, forming a subterranean ocean. Surface features include the large southern polar cap, older cratered planes cross-cut by graben and scarps, as well as youthful features caused by endogenic resurfacing. Because of its retrograde orbit and relative proximity to Neptune (closer than the Moon is to Earth), Triton is grouped with the planet’s irregular moons (see below). In addition, it is believed to be a captured object, possibly a dwarf planet that was once part of the Kuiper Belt.

At the same time, these orbital characteristics are the reason why Triton experiences tidal deceleration. and will eventually spiral inward and collide with the planet in about 3.6 billion years. Nereid is the third-largest moon of Neptune. It has a prograde but very eccentric orbit and is believed to be a former regular satellite that was scattered to its current orbit through gravitational interactions during Triton’s capture. Water ice has been spectroscopically detected on its surface. Nereid shows large, irregular variations in its visible magnitude, which are probably caused by forced precession or chaotic rotation combined with an elongated shape and bright or dark spots on the surface. Neptune’s Ring System: Neptune has five rings, all of which are named after astronomers who made important discoveries about the planet – Galle, Le Verrier, Lassell, Arago, and Adams. The rings are composed of at least 20% dust (with some containing as much as 70%) while the rest of the material consists of small rocks. The planet’s rings are difficult to see because they are dark and vary in density and size.

The Galle ring was named after Johann Gottfried Galle, the first person to see the planet using a telescope; and at 41,000–43,000 km, it is the nearest of Neptune’s rings. The La Verrier ring – which is very narrow at 113 km in width – is named after French astronomer Urbain Le Verrier, the planet’s co-founder. At a distance of between 53,200 and 57,200 km from Neptune (giving it a width of 4,000 km) the Lassell ring is the widest of Neptune’s rings. This ring is named after William Lassell, the English astronomer who discovered Triton just seventeen days after Neptune was discovered. The Arago ring is 57,200 kilometers from the planet and less than 100 kilometers wide. This ring section is named after Francois Arago, Le Verrier’s mentor and the astronomer who played an active role in the dispute over who deserved credit for discovering Neptune. The outer Adams ring was named after John Couch Adams, who is credited with the co-discovery of Neptune.

Although the ring is narrow at only 35 kilometers wide, it is the most famous of the five due to its arcs. These arcs accord with areas in the ring system where the material of the rings is grouped together in a clump, and are the brightest and most easily observed parts of the ring system. Although the Adams ring has five arcs, the three most famous are the “Liberty”, “Equality”, and “Fraternity” arcs. Scientists have been traditionally unable to explain the existence of these arcs because, according to the laws of motion, they should distribute the material uniformly throughout the rings. However, stronomers now estimate that the arcs are corralled into their current form by the gravitational effects of Galatea, which sits just inward from the ring. The rings of Neptune as seen from Voyager 2 during the 1989 flyby. Credit: NASA/JPL The rings of Neptune are very dark, and probably made of organic compounds that have been altered due to exposition to cosmic radiation. This is similar to the rings of Uranus, but very different to the icy rings around Saturn. They seem to contain a large quantity of micrometer-sized dust, similar in size to the particles in the rings of Jupiter.

It’s believed that the rings of Neptune are relatively young – much younger than the age of the Solar System, and much younger than the age of Uranus’ rings. Consistent with the theory that Triton was a KBO that was seized, by Neptune’s gravity, they are believed to be the result of a collision between some of the planet’s original moons. Exploration: The Voyager 2 probe is the only spacecraft to have ever visited Neptune. The spacecraft’s closest approach to the planet occurred on August 25th, 1989, which took place at a distance of 4,800 km (3,000 miles) above Neptune’s north pole. Because this was the last major planet the spacecraft could visit, it was decided to make a close flyby of the moon Triton – similar to what had been done for Voyager 1‘ s encounter with Saturn and its moon Titan . The spacecraft performed a near-encounter with the moon Nereid before it came to within 4,400 km of Neptune’s atmosphere on August 25th, then passed close to the planet’s largest moon Triton later the same day.

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. Neptune’s rotation period was determined using measurements of radio emissions and Voyager 2 also showed that Neptune had a surprisingly active weather system. Six new moons were discovered during the flyby, and the planet was shown to have more than one ring. While no missions to Neptune are currently being planned, some hypothetical missions have been suggested. For instance, a possible Flagship Mission has been envisioned by NASA to take place sometime during the late 2020s or early 2030s. Other proposals include a possible Cassini-Huygens -style “Neptune Orbiter with Probes”, which was suggested back in 2003. Another, more recent proposal by NASA was for Argo – a flyby spacecraft that would be launched in 2019, which would visit Jupiter, Saturn, Neptune, and a Kuiper belt object. The focus would be on Neptune and its largest moon Triton, which would be investigated around 2029.

With its icy-blue color, liquid surface, and wavy weather patterns, Neptune was appropriately named after the Roman god of the sea. And given its distance from our planet, there is still a great deal that remains to be learned about it. In the coming decades, one can only hope that a mission to the outer Solar System and/or Kuiper Belt includes a flyby of Neptune. We have many interesting articles about Neptune here at Universe Today. Below is a comprehensive list for your viewing (and possibly researching) pleasure! Characteristics of Neptune: Neptune - Educational facts and history of the planet Neptune. Neptune News Neptune Facts Neptune is the eighth planet from the Sun and the fourth largest (by diameter). Neptune is smaller in diameter but larger in mass than Uranus . Planet Profile orbit : 4,504,000,000 km (30.06 AU ) from Sun diameter : 49,532 km (equatorial) History of Neptune In Roman mythology Neptune (Greek: Poseidon ) was the god of the Sea. After the discovery of Uranus, it was noticed that its orbit was not as it should be in accordance with Newton 's laws.

It was therefore predicted that another more distant planet must be perturbing Uranus' orbit. Neptune was first observed by Galle and d'Arrest on 1846 Sept 23 very near to the locations independently predicted by Adams and Le Verrier from calculations based on the observed positions of Jupiter , Saturn and Uranus . An international dispute arose between the English and French (though not, apparently between Adams and Le Verrier personally) over priority and the right to name the new planet; they are now jointly credited with Neptune's discovery. Subsequent observations have shown that the orbits calculated by Adams and Le Verrier diverge from Neptune's actual orbit fairly quickly. Had the search for the planet taken place a few years earlier or later it would not have been found anywhere near the predicted location. More than two centuries earlier, in 1613, Galileo observed Neptune when it happened to be very near Jupiter, but he thought it was just a star. On two successive nights he actually noticed that it moved slightly with respect to another nearby star. But on the subsequent nights it was out of his field of view. Had he seen it on the previous few nights Neptune's motion would have been obvious to him.

But, alas, cloudy skies prevented observations on those few critical days. Neptune has been visited by only one spacecraft, Voyager 2 on Aug 25 1989. Much of we know about Neptune comes from this single encounter. But fortunately, recent ground-based and HST observations have added a great deal, too. Because Pluto 's orbit is so eccentric, it sometimes crosses the orbit of Neptune making Neptune the most distant planet from the Sun for a few years. Neptune's composition is probably similar to Uranus': various " ices " and rock with about 15% hydrogen and a little helium. Like Uranus, but unlike Jupiter and Saturn, it may not have a distinct internal layering but rather to be more or less uniform in composition. But there is most likely a small core (about the mass of the Earth) of rocky material. Its atmosphere is mostly hydrogen and helium with a small amount of methane. Neptune's blue color is largely the result of absorption of red light by methane in the atmosphere but there is some additional as-yet-unidentified chromophore which gives the clouds their rich blue tint. Like a typical gas planet , Neptune has rapid winds confined to bands of latitude and large storms or vortices.

Neptune's winds are the fastest in the solar system, reaching 2000 km/hour. Like Jupiter and Saturn, Neptune has an internal heat source -- it radiates more than twice as much energy as it receives from the Sun. At the time of the Voyager encounter, Neptune's most prominent feature was the Great Dark Spot (left) in the southern hemisphere. It was about half the size as Jupiter's Great Red Spot (about the same diameter as Earth). Neptune's winds blew the Great Dark Spot westward at 300 meters/second (700 mph). Voyager 2 also saw a smaller dark spot in the southern hemisphere and a small irregular white cloud that zips around Neptune every 16 hours or so now known as "The Scooter" (right). It may be a plume rising from lower in the atmosphere but its true nature remains a mystery. However, HST observations of Neptune (left) in 1994 show that the Great Dark Spot has disappeared! It has either simply dissipated or is currently being masked by other aspects of the atmosphere. A few months later HST discovered a new dark spot in Neptune's northern hemisphere.

This indicates that Neptune's atmosphere changes rapidly, perhaps due to slight changes in the temperature differences between the tops and bottoms of the clouds. Neptune also has rings. Earth-based observations showed only faint arcs instead of complete rings, but Voyager 2 's images showed them to be complete rings with bright clumps. One of the rings appears to have a curious twisted structure (right). Like Uranus and Jupiter, Neptune's rings are very dark but their composition is unknown. Neptune's rings have been given names: the outermost is Adams (which contains three prominent arcs now named Liberty, Equality and Fraternity), next is an unnamed ring co-orbital with Galatea, then Leverrier (whose outer extensions are called Lassell and Arago), and finally the faint but broad Galle. Neptune's magnetic field is, like Uranus', oddly oriented and probably generated by motions of conductive material (probably water) in its middle layers. Neptune can be seen with binoculars (if you know exactly where to look) but a large telescope is needed to see anything other than a tiny disk.

There are several Web sites that show the current position of Neptune (and the other planets) in the sky, but much more detailed charts will be required to actually find it. Such charts can be created with a planetarium program . Neptune's Satellites Data on the newly discovered moons can be found at JPL and Scott Sheppard's site . Open Issues Neptune's magnetic field is off center and at a large angle to its rotation axis. What processes in the interior generate this oddly shaped field? What accounts for the relative lack of hydrogen and helium in Neptune (and Uranus)? Why are Neptune's winds so strong in spite of the fact that it is so far from the Sun and has a relatively weak internal heat source? What happened to the Great Dark Spot? Can we design a useful Neptune orbiter mission cheap enough to be funded? The Rings of Neptune - Universe Today Universe Today by Fraser Cain Neptune is one of four planets in our Solar System with planetary rings. Neptune was not discovered until 1846 and its rings were only discovered definitively in 1989 by the Voyager 2 probe.

Although the rings were not discovered until the late 1900’s, William Lassell who discovered Titan recorded that he had observed a ring. However, this was never confirmed. The first ring was actually discovered in 1968, but scientists were unable to determine if it was a complete ring. The Voyager’s evidence was the definitive proof for the existence of the rings. Neptune has five rings: Galle, Le Verrier, Lassell, Arago, and Adams. Its rings were named after the astronomers who made an important discovery regarding the planet. The rings are composed of at least 20% dust with some of the rings containing as much as 70% dust; the rest of the material comprising the rings is small rocks. The planet’s rings are difficult to see because they are dark and vary in density and size. Astronomers think Neptune’s rings are young compared to the age of the planet, and that they were probably formed when one of Neptune’s moons was destroyed. The Galle ring was named after Johann Gottfried Galle, the first person to see the planet using a telescope.

It is the nearest of Neptune’s rings at 41,000–43,000 km. The La Verrier ring was named after the man who predicted Neptune’s position. Very narrow, this ring is only about 113 kilometers wide. The Lassell ring is the widest of Neptune’s rings. Named after William Lassell, it lies between 53,200 kilometers and 57,200 kilometers from Neptune, making it 4,000 kilometers wide. The Arago ring is 57,200 kilometers from the planet and less than 100 kilometers wide. The outer ring, Adams, was named after John Couch Adams who is credited with the co-discovery of Neptune. Although the ring is narrow at only 35 kilometers wide, it is the most famous of the five due to its arcs. Adams’ arcs are areas where the material of the rings is grouped together in a clump. Although the Adams ring has five arcs, the three most famous ones are Liberty, Equality, and Fraternity. The arcs are the brightest parts of the rings and the first to be discovered.

Scientists are unable to explain the existence of these arcs because according to the laws of motion they should distribute the material uniformly throughout the rings. The rings of Neptune are very dark, and probably made of organic compounds that have been baked in the radiation of space. This is similar to the rings of Uranus, but very different to the icy rings around Saturn. They seem to contain a large quantity of micrometer-sized dust, similar in size to the particles in the rings of Jupiter. It’s believed that the rings of Neptune are relatively young – much younger than the age of the Solar System, and much younger than the age of Uranus’ rings. They were probably created when one of Neptune’s inner moons got to close to the planet and was torn apart by gravity. The innermost ring of Neptune orbits at a distance of 41,000 km from the planet, and extends to a width of 2,000 km. It’s named after Johann Gottfried Galle, the first person to see Neptune through a telescope. The next ring is the narrower LeVerrier ring, named after Neptune’s co-discoverer, Urbain Le Verrier. It’s only 113 km wide.

Then comes the Lassell ring, the widest ring in the system at about 4,000 km. Then comes the Arago ring, and finally the very thin Adams ring, named after Neptune’s other co-discoverer. If you’d like more information on Neptune, take a look at Hubblesite’s News Releases about Neptune , and here’s a link to NASA’s Solar System Exploration Guide to Neptune . We have recorded an entire episode of Astronomy Cast just about Neptune. You can listen to it here, Episode 63: Neptune . 15 Interesting Facts About Neptune That'll Rock You to the Core Follow Us 15 Interesting Facts About Neptune That'll Rock You to the Core How was Neptune discovered? How did it get its name? What is Neptune composed of? Which color is Neptune? How many moons and rings does it have? Advertisement Neptune, also known as the 'Blue Giant' is the eighth planet from the Sun, situated between Uranus and Pluto. However, sometimes Pluto is seen to cross its path, and then it becomes the ninth planet from the Sun.

Neptune is 49500 km in diameter, and is four times the size of the Earth, however, since it is approximately 4.4 billion km away from the Earth, it is not easily visible through binoculars. How was Neptune discovered? In case of the other planets, telescopes found them, however, in case of Neptune, the mathematical calculations lead to the planet's discovery. Several astronomers, including Galileo had seen Neptune, little realizing that they were looking at another planet. This was because, through the telescopes, planets appeared to look like discs, and stars appeared as spots of bright light. The telescopes were not powerful enough to show Neptune's disc shape. In 1781, William Hershel discovered planet Uranus and after Uranus' discovery, astronomers began to wonder if there was another planet beyond Uranus. In 1843, John C. Adams, a young British mathematician and astronomer set forth to calculate the position of Neptune. According to his calculations, Neptune was 1 billion miles further away from the Sun, than Uranus. He sent his findings to the astronomer royal of England, Sir George B Airy, in 1845.

But to Adams dismay, Airy did not respond to his findings. However, Adams was not the only one working on Neptune's calculations. Urbain Jean Joseph Le Verrier, a French astronomer and mathematician was also diligently calculating the location of Neptune. In 1846, he too came up with the same results as Adams, and sent his findings to Johann G. Galle of Germany. Galle had also been working on the location of the planets, and with the help of Urbain's predictions, he along with his assistant found the planet Neptune on September 23rd 1846. However, after the discovery, conflicts between UK and France arose, over who should be credited with the discovery of Neptune. The international astronomy community decided to give the credit to both Adams and Urbain for Neptune's discovery. Isn't this an interesting fact about Neptune? How did Neptune get its name? Neptune is the Roman counterpart of the Greek God Poseidon The naming ceremony of Neptune has an interesting story. Urbain J.J. Le Verrier felt that since he discovered the planet, he had the right to name it after himself. However, his desire was trampled by people outside France.

Since, all the other planets were named after Roman Gods, the international astronomy community came to a consensus that this planet should also be named after a Roman God. Thus, Neptune, being a blue planet was named after the Roman God of the sea. Composition of Neptune The mantle region is extremely hot, with temperatures ranging from 3000K to 5000K Neptune's hot rocky core is approximately the size of the earth and is made up of nickel, iron and other silicates. Beyond the core, is the large mantle comprising methane, ammonia, water and other compounds. This mantle region is extremely hot, with temperatures ranging from 3000K to 5000K, thus this region corresponds to a superheated liquid region. Beyond the mantle is the outermost atmosphere which is made up of gases like Hydrogen (80%), Helium (19%) and (1%) Methane, Ammonia and water. Neptune: The Windiest Planet The energy to generate these winds comes from Neptune's internal heat source Neptune has extraordinary weather and is the most windy planet in our solar system.

Logically speaking planets further away from the Sun must have weaker winds, because wind is driven by the Sun's energy and planets that receive less sunlight should have weaker winds. However, Neptune has extremely strong winds, which can reach speeds of about 2,000 kilometers per hour. A hurricane on earth would approximately reach a speed of 200 kilometer per hour, so one can imagine the magnitude of these wind storms. The energy to generate these winds comes from Neptune's internal heat source. Why is Neptune blue in color? Neptune's color is nothing but reflected sunlight minus red end of the spectrum Neptune is a gas planet (like Jupiter, Saturn and Uranus), and its upper atmosphere is made up of gases such as Hydrogen, Helium, Methane, Ammonia, and water. Methane on Neptune's surface absorbs light coming from the Sun at 600nm, which corresponds to the red region of the visible light spectrum. Therefore, methane absorbs red light and reflects blue end of the spectrum back into space. This is how Neptune gets its azure blue color.

Weather Patterns on Neptune Neptune with The Great Dark Spot As per the information obtained from Voyager 2's visit to Neptune in 1989, Neptune exhibits distinct weather patterns. It observed an extremely massive anticyclonic storm system, which appeared as a massive dark spot on the surface (southern hemisphere) of the planet. The series of dark spots observed is known as the Great Dark Spot, of which the largest corresponds to the size the Earth. This Great Dark Spot is surrounded by white cirrus clouds of methane. Then Voyager 2 also spotted smaller spots, called scooters, which move rapidly across the surface of the planet. Moons of Neptune Neptune and its first moon, Triton 17 days after the planet Neptune was discovered, an astronomer named William Lassell discovered Neptune's first moon, Triton. Triton is 2707 km in diameter, and had it been orbiting the Sun, instead of Neptune, then it could have been called a planet. The orbit of Triton is retrograde, which means it orbits in the opposite direction to the planet's rotation. This is also indicative of the fact that Neptune actually captured Triton.

An interesting fact about Neptune's Triton is that Triton's surface temperature is only 38 Kelvin, which makes Triton one of the coldest regions of the solar system. Voyager 2 (USA) visited Neptune in 1989, and is the only spacecraft to have visited the planet. It discovered geysers of blasting nitrogen on Triton's surface. Even though it took only seventeen days after the planet's discovery to find Triton, the second moon was discovered only 100 years later, in 1949. As of today, 13 of Neptune's moons have been discovered, all of which are named after Gods from Greek mythology. Rings of Neptune The 5 rings are named Galle, Le Verrier, Lassell, Arago, and Adams With the help of the images captured by Voyager 2, we have come to know that Neptune possesses 5 faint rings. These 5 rings are named Galle, Le Verrier, Lassell, Arago, and Adams: astronomers who were involved with discoveries related to Neptune. These rings are relatively new to the Solar System, and are younger than Uranus' rings.

Astronomers believe that the rings were formed when one of Neptune's moons got too close to the planet and disintegrated due to gravity. Length of Day and Year on Neptune While Earth takes 365 days to complete a revolution round the sun, Neptune takes 60,190 days What's interesting about Neptune is that different parts of the planet rotate at a different pace. The polar regions of the planet take 12 hours to complete one rotation, whereas the equatorial region takes 18 hours to complete one rotation. On an average, the planet takes 16 hours to complete a day. A day on Neptune is shorter than a day on the Earth, however, a year on Neptune is longer than a year on the Earth. This is because Neptune orbits the Sun at an average distance of 4.5 billion kilometers. Where the Earth takes 365 days to complete one rotation, Neptune takes 60,190 days to revolve around the Sun once. So a year on Neptune is 165 Earth years. Water is present on Neptune, so is there a possibility of life on Neptune?

Scientists say that since there is water, technically life should exist, however, the surface of Neptune is far too cold for any living organism to exist (water turns to ice). But, the planet gets hotter towards the core, so can life exist at the point at which the planet is neither too hot, nor too cold (where water exists in liquid form). This is still something scientists are working on. Till they come up with the answer, we can cling on to these interesting facts about Neptune. Priya Johnson The Nine Planets Glossary Adams, John Couch 1819-1892 English astronomer and mathematician who, at the age of 24, was the first person to predict the position of a planetary mass beyond Uranus . But, unfortunately, Adams did not publish his prediction. Galle confirmed the existence of Neptune based on independent calculations done by Le Verrier . ( 4k jpg ) albedo the ratio of the amount of light reflected by an object and the amount of incident light; a measure of the reflectivity or intrinsic brightness of an object (a white, perfectly reflecting surface would have an albedo of 1.0; a black perfectly absorbing surface would have an albedo of 0.0).

Keeler, James E. 1857-1900 American astrophysicist, probable discoverer of the dark narrow gap in the outer part of the A ring of Saturn , and the second director of Lick Observatory . Keeler was (probably accidentally) cheated of his rightful fame when the A ring gap became known as "Encke's Division". Encke had earlier seen a broad, poor contrast feature in the A-ring which is quite different from the sharp, distinct gap that Keeler recorded on the very first night of observing with the Lick 36-inch refractor. On the other hand, the gap may have been seen even earlier by Francesco De Vico, William Lassell and the Rev. William R. Dawes. The history of visual observations of gaps in Saturn's rings is very confusing. French (originally Italian, Giuseppe Luigi Lagrangia; born in Turin, moved to Paris and became a French citizen) mathematician and astronomer; made a number of contributions to the study of celestial mechanics. ( 5k gif ) Lagrange points Lagrange showed that three bodies can lie at the apexes of an equilateral triangle which rotates in its plane.

If one of the bodies is sufficiently massive compared with the other two, then the triangular configuration is apparently stable. Bodies at such points are sometimes referred to as Trojans . The leading apex of the triangle is known as the leading Lagrange point or L4; the trailing apex is the trailing Lagrange point or L5. Collinear with the two large bodies are the L1, L2 and L3 unstable equilibrium points which can sometimes be useful places for spacecraft, eg SOHO . ( more and more ) magnitude The degree of brightness of a celestial body designated on a numerical scale, on which the brightest star has magnitude -1.4 and the faintest visible star has magnitude 6, with the scale rule such that a decrease of one unit represents an increase in apparent brightness by a factor of 2.512. Also called apparent magnitude. mare literally "sea" (a very bad misnomer, still in use for historical reasons); really a large circular plain Marius, Simon 1573-1624 (a.k.a. Mayr) German astronomer who gave Jupiter 's " Galilean " moons their names.

He and Galileo both claimed to have discovered them in 1610 and likely did so independently. Marius was also the first to observe the Andromeda Nebula with a telescope and one of the first to observe sunspots . ( more ) mensa Oort, Jan Hendrik 1900-1992 Dutch astronomer made major contributions to knowledge of the structure and rotation of our galaxy. More or less as a sideline, Oort studied comets as well. The result of this work was a theory, now widely accepted, that the Sun is surrounded by a distant cloud of comet-stuff, now called the Oort cloud , bits of which are occasionally hurled into the solar system as comets. ( more ; 142k gif ) opposition A superior planet is said to be "in opposition" when it is directly on the opposite side of the Earth from the Sun. This is generally the closest it comes to the Earth and the time at which it is most easily visible. ( nice diagram ) retrograde rotation or orbital motion in a clockwise direction when viewed from above the north pole of the primary (i.e. in the opposite sense to most satellites); the opposite of direct .

The north pole is the one on the same side of the ecliptic as the Earth's north pole. an elongated valley formed by the depression of a block of the planet's crust between two faults or groups of faults of approximately parallel strike. rima Roche limit the closest a fluid body can orbit to its primary without being pulled apart by tidal forces. A solid body may survive within the Roche limit if the tidal forces do not exceed its structural strength. The Roche limit is calculated with the equation RL = 2.456*R*(p'/p)^(1/3) where p' is the density of the planet, p is the density of the moon, and R is the radius of the planet. ( more ) rupes Schiaparelli, Giovanni Virginio 1835-1910 Italian astronomer who in 1877 first observed the "canals" on Mars . He believed that the features he observed included straight lines that joined in a complicated pattern. He called these lines 'canali', which means 'channels'. However, the Italian word was mistranslated into the English word 'canals'.

That, combined with the suspicious straightness of the lines, bespoke of artificial structures, and this created a furor. Speculations concerning the possibility of intelligent life on Mars sprang up in the popular press. Even astronomers felt the pull of that dramatic possibility. Foremost among these was Percival Lowell , who carried matters far beyond Schiaparelli. scopulus semimajor axis the semimajor axis of an ellipse (e.g. a planetary orbit) is 1/2 the length of the major axis which is a segment of a line passing thru the foci of the ellipse with endpoints on the ellipse itself. The semimajor axis of a planetary orbit is also the average distance from the planet to its primary. The periapsis and apoapsis distances can be calculated from the semimajor axis and the eccentricity by rp = a(1-e) and ra = a(1+e). = 299,792,458 meters/second (186,000 miles/second). Einstein 's Theory of Relativity implies that nothing can go faster than the speed of light; Scotty and Geordi know better.

spicules stellar classification Stars given a designation consisting of a letter and a number according to the nature of their spectral lines which corresponds roughly to surface temperature. The classes are: O, B, A, F, G, K, and M; O stars are the hottest; M the coolest. The numbers are simply subdivisions of the major classes. The classes are oddly sequenced because they were assigned long ago before we understood their relationship to temperature. O and B stars are rare but very bright; M stars are numerous but dim. The Sun is designated G2. to change directly from a solid to a gas without becoming liquid sulcus an area seen as a dark spot on the photosphere of the Sun ; sunspots are concentrations of magnetic flux, typically occurring in bipolar clusters or groups; they appear dark because they are cooler than the surrounding photosphere. superior planets the planets Mars , Jupiter , Saturn , Uranus , Neptune and Pluto are called superior planets because their orbits are farther from the Sun than Earth's orbit. (Mercury and Venus are called " inferior " planets.) synchronous orbit radius the orbital radius at which the satellite's orbital period is equal to the rotational period of the planet.

A synchronous satellite with an orbital inclination of zero (same plane as the planet's equator) stays fixed in the sky from the perspective of an observer on the planet's surface (such orbits are commonly used for communications satellites). synchronous rotation said of a satellite if the period of its rotation about its axis is the same as the period of its orbit around its primary. This implies that the satellite always keeps the same hemisphere facing its primary (e.g. the Moon ). It also implies that one hemisphere (the leading hemisphere) always faces in the direction of the satellite's motion while the other (trailing) one always faces backward. Most of the satellites in the solar system rotate synchronously.

kmhouseindia: Rings of Neptune Sunday, May 15, 2016 Rings of Neptune The Rings of Neptune consist primarily of five principal rings and were first discovered (as "arcs") in 1984 They were eventually imaged in 1989 by the Voyager 2 spacecraft Neptune possesses five distinct rings named, in order of increasing distance from the planet, Galle, Le Verrier, Lassell, Arago and Adams Three of the Neptunian rings are narrow, with widths of about 100 km or less;in contrast, the Galle and Lassell rings are broad—their widths are between 2,000 and 5,000 km Posted by Glossaire Adams, John Couch 1819-1892 English astronomer and mathematician who, at the age of 24, was the first person to predict the position of a planetary mass beyond Uranus . But, unfortunately, Adams did not publish his prediction. Galle confirmed the existance of Neptune based on independent calculations done by Le Verrier .

( 4k jpg ) albédo the ratio of the amount of light reflected by an object and the amount of incident light; a measure of the reflectivity or intrinsic brightness of an object (a white, perfectly reflecting surface would have an albedo of 1.0; a black perfectly absorbing surface would have an albedo of 0.0). Lagrange, Joseph Louis 1736-1813 French (originally Italian, Giuseppe Luigi Lagrangia; born in Turin, moved to Paris and became a French citizen) mathematician and astronomer; made a number of contributions to the study of celestial mechanics. Lagrange showed that three bodies can lie at the apexes of an equilateral triangle which rotates in its plane. If one of the bodies is sufficiently massive compared with the other two, then the triangular configuration is apparently stable. Such bodies are sometimes refered to as Trojans . The leading apex of the triangle is known as the leading Lagrange point or L4; the trailing apex is the trailing Lagrange point or L5.

( see also ) ( 5k gif ) magnitude The degree of brightness of a celestial body designated on a numerical scale, on which the brightest star has magnitude -1.4 and the faintest visible star has magnitude 6, with the scale rule such that a decrease of one unit represents an increase in apparent brightness by a factor of 2.512. Also called apparent magnitude. mare literally "sea" (a very bad misnomer, still in use for historical reasons); really a large circular plain Marius, Simon 1573-1624 (a.k.a. Mayr) German astronomer who gave Jupiter 's " Galilean " moons their names. He and Galileo both claimed to have discovered them in 1610 and likely did so independently. They become involved in a dispute over priority. Marius was also the first to observe the Andromeda Nebula with a telescope and one of the first to observe sunspots . ( more ) mensa rétrograde rotation or orbital motion in a clockwise direction when viewed from the north pole of the primary (i.e. in the opposite sense to most satellites); the opposite of direct .

The north pole is the one on the same side of the ecliptic as the Earth's north pole. an elongated valley formed by the depression of a block of the planet's crust between two faults or groups of faults of approximately parallel strike. rima Roche limit the closest a fluid body can orbit to its primary without being pulled apart by tidal forces. A solid body may survive within the Roche limit if the tidal forces do not exceed its structural strength. The Roche limit is calculated with the equation RL = 2.456*R*(p'/p)^(1/3) where p' is the density of the planet, p is the density of the moon, and R is the radius of the planet. ( more ) rupes Schiaparelli, Giovanni Virginio 1835-1910 Italian astronomer who in 1877 first observed the "canals" on Mars . He believed that the features he observed included straight lines that joined in a complicated pattern. He called these lines 'canali', which means 'channels'. However, the Italian word was mistranslated into the English word 'canals'.

That, combined with the suspicious straightness of the lines, bespoke of artificial structures, and this created a furor. Speculations concerning the possibility of intelligent life on Mars sprang up in the popular press. Even astronomers felt the pull of that dramatic possibility. Foremost among these was Percival Lowell , who carried matters far beyond Schiaparelli. scopulus semimajor axis the semimajor axis of an ellipse (e.g. a planetary orbit) is 1/2 the length of the major axis which is a segment of a line passing thru the foci of the ellipse with endpoints on the ellipse itself. The semimajor axis of a planetary orbit is also the average distance from the planet to its primary. The periapsis and apoapsis distances can be calculated from the semimajor axis and the eccentricity by rp = a(1-e) and ra = a(1+e). = 299,792,458 meters/second (186,000 miles/second). Einstein 's Theory of Relativity implies that nothing can go faster than the speed of light; Scotty and Geordi know better.

spicules stellar classification Stars given a designation consisting of a letter and a number according to the nature of their spectral lines which corresponds roughly to surface temperature. The classes are: O, B, A, F, G, K, and M; O stars are the hottest; M the coolest. The numbers are simply subdivisions of the major classes. The classes are oddly sequenced because they were assigned long ago before we understood their relationship to temperature. O and B stars are rare but very bright; M stars are numerous but dim. The Sun is designated G2. to change directly from a solid to a gas without becoming liquid sulcus an area seen as a dark spot on the photosphere of the Sun ; sunspots are concentrations of magnetic flux, typically occurring in bipolar clusters or groups; they appear dark because they are cooler than the surrounding photosphere. superior planets synchronous orbit radius the orbital radius at which the satellite's orbital period is equal to the rotational period of the planet. A synchronous satellite with an orbital inclination of zero (same plane as the planet's equator) stays fixed in the sky from the perspective of an observer on the planet's surface (such orbits are commonly used for communications satellites).

synchronous rotation said of a satellite if the period of its rotation about its axis is the same as the period of its orbit around its primary. This implies that the satellite always keeps the same hemisphere facing its primary (e.g. the Moon ). It also implies that one hemisphere (the leading hemisphere) always faces in the direction of the satellite's motion while the other (trailing) one always faces backward. Most of the satellites in the solar system rotate synchronously.

Question: Galle, Le Vernier, Lassell, Arago and Adams are all rings round which planet?
Answer: Neptune