Neptune has a known 14 months, which is named the little water god in Greek mythology. By far the largest of them is Triton, discovered by William Lassell on October 10, 1846, 17 days after the discovery of Neptune itself; more than a century passed before the discovery of the second natural satellite, Nereid. The outer moons of Neptune, Neso, which has an orbital period of about 26 Julian years, orbits further from its planet than any other month in the Solar System.
Triton is unique among the planet's mass moons in its orbit that retreat to Neptune's rotation and tends to be relative to the Neptune's equator, indicating that it does not form in orbit around Neptune but instead is gravitatively captured by it. The next largest irregular satellite in the Solar System, the moon of Saturn Phoebe, has only 0.03% of the Triton mass. Triton's capture, perhaps some time after Neptune formed a satellite system, was a catastrophic event for Neptune's native satellite, disrupting its orbit so that they collided to form debris. Tritons are large enough to achieve a hydrostatic balance and maintain a thin atmosphere capable of forming clouds and fog.
Inside the Triton there are seven small regular satellites, all of which have prograde orbits on planes located close to the equatorial plane of Neptune; some of these orbits are in between Neptune's rings. The greatest of them is Proteus. They returned from the rubble disk that was produced after Triton's capture after the Tritonian orbit became a circle. Neptune also has six other irregular satellites besides Triton, including Nereid, whose orbit is much farther from Neptune and on a high tendency: three of them have prograde orbits, while the rest have retrograde orbits. In particular, Nereid has an extraordinarily close and eccentric orbit for irregular satellites, indicating that the satellite was once a regular satellite that was significantly disrupted by its current position when Triton was captured. Two irregular Neptune satellites, Psamathe and Neso, have the largest orbits of any natural satellite found in the Solar System to date.
Video Moons of Neptune
Histori
Discovery
Triton was discovered by William Lassell in 1846, just seventeen days after the discovery of Neptune. Nereid was invented by Gerard P. Kuiper in 1949. The third month, later named Larissa, was first observed by Harold J. Reitsema, William B. Hubbard, Larry A. Lebofsky and David J. Tholen on May 24, 1981. Astronomers were observing approaches the star to Neptune, looking for rings similar to those found around Uranus four years earlier. If a ring is present, the luminosity of the star will decrease slightly just before the closest approximation of the planet. The star's luminosity only dips for a few seconds, which means it's due to the moon rather than the ring.
No more moons were discovered until Voyager 2 flew by Neptune in 1989. Voyager 2 rediscovered Larissa and discovered five inner moons: In 2001, two surveys using large ground-based telescopes found five extra outer months, bringing the total to thirteen. Follow-up surveys by two teams in 2002 and 2003 each again observed the fifth of this month, namely Halimede, Sao, Psamathe, Laomedeia, and Neso. The sixth month of the candidate was also found in the 2002 survey and disappeared after that: perhaps the centaur is not a satellite, although its relatively small number of moves against Neptune for a month indicates that the satellite is true. It is estimated to have a diameter of 33 km and about 25.1 million won (0.168 AU) of Neptune when it is found.
Name
Triton has no official name until the 20th century. The name "Triton" was suggested by Camille Flammarion in his book in 1880 Astronomie Populaire , but it is not commonly used until at least the 1930s. Until now it is commonly known simply as the "Neptune satellite". Other moons Neptune is also named after the Greek and Roman water gods, according to the position of Neptune as the god of the sea: both of Greek mythology, usually the children of Poseidon, Greek Neptune (Triton, Proteus, Despina, Thalassa); lovers of Poseidon (Larissa); class of Greek small water gods (Naiad, Nereid); or certain Nereids (Halimede, Galatea, Neso, Sao, Laomedeia, Psamathe). For "irregular" normal satellites, this convention uses names ending in "a" for prograde satellites, names ending in "e" for retrograde satellites, and names ending in "o" for highly tilted satellites, just like convention for Jupiter month. The two asteroids share the same name with the moon Neptune: 74 Galatea and 1162 Larissa.
Maps Moons of Neptune
Characteristics
The moons of Neptune can be divided into two groups: regular and irregular. The first group includes seven deep moons, which follow a circular progressive orbit located in the equatorial plane of Neptune. The second group consists of seven other months including Triton. They generally follow an eccentrically inclined orbit and often retreat from Neptune; the only exception is the Triton, which orbits near the planet following a circular orbit, albeit backward and tilted.
Regular month
Within the distance from Neptune, the usual moons are Naiad, Thalassa, Despina, Galatea, Larissa, S/2004 N 1, and Proteus. All but two outer sections are in synchronous Neptune orbit (Neptune's rotation period is 0.6713 days) and thus is being slowly slowed down. Naiad, the closest regular month, is also the second smallest among the deep months (after the discovery of S/2004 N 1), while Proteus is the largest regular month and the second largest month of Neptune.
The inner moons are closely related to the Neptune ring. The two deepest satellites, Naiad and Thalassa, orbit between Galle and LeVerrier rings. Despina is probably the shepherd moon of the LeVerrier ring, because its orbit lies right inside this ring. The next month, Galatea, orbits right inside the most prominent ring of Neptune, the Adams ring. This ring is very narrow, with a width not exceeding 50 km, and has five embedded bright arcs. Galatea's gravity helps limit the particles of the ring within a restricted region in the radial direction, maintaining a narrow ring. The various resonances between the ring particles and Galatea may also have a role in maintaining the arc.
Only the two largest regular moons have been imaged with enough resolution to distinguish the shape and surface features. Larissa, about 200 km in diameter, extends. Proteus does not elongate significantly, but is not completely round either: it resembles an irregular polyhedron, with some flat sides or slightly sunken diameter of 150 to 250 sq. Km. At about 400 km in diameter, it is larger than Saturn Mimas' moons, which are entirely ellipsoidal. This difference may be due to impaired Proteus disorders in the past. The Proteus surface is very crater and shows a number of linear features. The largest crater, Pharos, is more than 150 km in diameter.
All the moons in Neptune are dark objects: their geometric albedo ranges from 7 to 10%. Their spectrum shows that they are made of ice water that is contaminated by some very dark material, perhaps a complex organic compound. In this case, the inner moon of Neptune is similar to that of the inner Uranus.
The moon is irregular
In the order of their distance from the planet, the irregular months are Triton, Nereid, Halimede, Sao, Laomedeia, Psamathe, and Neso, groups that include prograde and retrograde objects. The five outermost moons resemble the other monster moons of the other planets, and are thought to have been gravitated by Neptune, unlike ordinary satellites, which may have formed in situ.
Triton and Nereid are unusual irregular satellites and are therefore treated separately from five other irregular Neptune moons, which are more like irregular outer satellites than other outer planets. First, they are the two largest regular moon known in the Solar System, with Triton almost a sequence of magnitudes larger than all other known irregular moons. Second, they both have a small atypical semi-main ax, with Triton at the top of an order of magnitude smaller than all other known irregular moons. Third, they both have an unusual eccentricity of orbital: Nereid has one of the most eccentric orbits of known irregular satellites, and the orbit of Triton is an almost perfect circle. Finally, Nereid also has the lowest tendency of known irregular satellites.
Triton
The triton follows retrograde and quasi-circular orbit, and is considered a satellite that is captured by gravity. It is the second month in the Solar System that is found to have a substantial atmosphere, which is mainly nitrogen with a small amount of methane and carbon monoxide. The pressure on the Triton surface is about 14Ã, bar. In 1989, the spacecraft Voyager 2 watched what looked like clouds and fog in this thin atmosphere. Triton is one of the coldest bodies in the Solar System, with a surface temperature of about 38Ã,K (-235,2Ã, Â ° C). Its surface is covered by nitrogen, methane, carbon dioxide and ice water and has a high geometric albedo over 70%. The albedo Bond is even higher, reaching up to 90%. Surface features include large south polar caps, older crater planes cut into pieces by graben and scarps, as well as young features that may be formed by endogenous processes such as cryovolcanism. Voyager 2 observations reveal a number of active geysers inside a solar cap heated by the Sun, which releases clumps up to a height of up to 8 km. Triton has a relatively high density of about 2 g/cm 3 indicating that the rock is about two thirds of its mass, and ice (especially ice water) is left one-third. There may be a layer of liquid water deep within the Triton, forming an underground sea. Because of its retrograde orbit and relatively close to Neptune (closer than the Moon to Earth), tidal decelerations caused Triton to shift inward, which would cause its destruction of about 3.6 billion years.
Nereid
Nereid is the third largest Neptune month. It has a prograde but its orbit is very eccentric and it is believed to be an ordinary satellite that is dispersed into its current orbit through gravitational interactions during Triton's capture. Water ice has been detected spectroscopically on its surface. Initial measurements Nereid exhibits large and irregular variations in visible magnitudes, which are thought to be caused by forced or chaotic rotation combined with the elongated shape and bright or dark spots on the surface. This is denied in 2016, when observations from the Kepler space telescope show only slight variations. Thermal modeling based on infrared observations from the Spitzer and Herschel space telescopes shows that Nereid is only slightly elongated that disrupts the precession of rotation. The thermal model also shows that Nereid surface roughness is very high, possibly similar to Hionion Moon Saturn.
Normal month is not regular
Among the remaining irregular months, Sao and Laomedeia follow a prograde orbit, while Halimede, Psamathe and Neso follow a retrograde orbit. Given the similarity of its orbit, it is suggested that Neso and Psamathe could have the same origin in breaking the larger moon. Psamathe and Neso have the greatest orbit of any natural satellite found in the solar system to date. It took them 25 years to orbit Neptune with an average of 125 times the distance between Earth and the Moon. Neptune has the largest Hill ball in the Solar System, mainly because it is far from the Sun; this allowed him to maintain control of the distant moon. Nevertheless, Jupiter S/2003 J 2 orbits at the greatest percentage of the primary Hill radius of all months in the Solar System on average, and the Jovian moons in the Carme and Pasiphae groups orbit at a greater percentage than their primary Hill radius Psamathe and Neso.
Formation
The moon mass distribution of Neptune is the most oblique of the giant planetary satellite systems in the Solar System. One month, Triton, makes up almost any system mass, with all the other months together comprising only one-third of one percent. This is similar to the Saturn moon system, where Titan makes up more than 95% of the total mass, but is different from the more balanced Jupiter and Uranus systems. The reason for the slope of Neptune's current system is that Triton was captured well after the formation of Neptune's native satellite system, most of which will be destroyed in the process of capture.
The Triton orbit on capture will be very eccentric, and will cause a chaotic interruption in the orbit of Neptune's satellites in the original, causing them to collide and decrease into a disc of debris. This means the possibility that the satellites in Neptune present are not native bodies formed with Neptune. Only after Triton's orbit has been circulated, perhaps some of the ruins will return to the regular months of today. This major disturbance may be the reason why the Neptune satellite system does not follow the 10,000: 1 mass ratio between the mother planet and all the moons seen in satellite systems of all the other giant planets.
The Triton capture mechanism has been the subject of several theories over the years. One of them postulates that Triton was arrested in a three-body meeting. In this scenario, Triton is a surviving member of the Kuiper binary belt object that is interrupted by its encounter with Neptune.
Numerical simulations show that there is a probability of 0.41 that Halimede's moon collided with Nereid at a time in the past. Although it is not known whether there is a collision occurring, the two months seem to have the same color ("gray"), implying that Halimede could be part of Nereid.
List
The Moon of Neptune is listed here by the orbital period, from the shortest to the longest. Irregular rays (captured) are marked with color. Triton, the only massive moon of Neptune since its surface has collapsed into a spheroid, is becoming bolder.
Note
References
External links
- Neptune Known Satellite
- Neptune Month by NASA Solar System Exploration
- Gazetteer of Planetary Nomenclature - Neptune (USGS)
- A simulation showing the position of the Neptune Moon
- 13 Months of Neptune - Astronoo
Source of the article : Wikipedia
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