The mysterious and distant Neptune has been known to astronomers for more than one hundred and seventy years. His discovery was the triumph of theoretical science. Despite the development of instrumental astronomy and unmanned astronautics, the planet holds many secrets, and the unusual orbit of the satellite of Neptune - Triton is still the subject of debate and hypotheses.
Janus? Neptune!
Initially, the eighth planet of the solar system wanted to give the name of the ancient Roman god of beginning and end - Janus. According to the discoverers, it was this cosmic body that personified the end of the "possessions" of our star, and the beginning of unlimited outer space. And the scientists who discovered the planet really were a few.
It all started with the fact that in 1834 a priest from England, madly fascinated by astronomy, T.D. Hassi, was very surprised to observe the recently discovered planet Uranus that its true trajectory in the celestial sphere does not coincide with the calculated one. The Holy Father suggested that this deviation was caused by the influence of a massive space object located beyond the orbit of the gas giant.
Who should be considered a discoverer?
The British scientist D.K. Adams and the Frenchman W.J. Le Verrier independently calculated the approximate position of the unknown body. According to the indicated coordinates, the German astronomer I. G. Halle (Berlin Observatory) and his assistant G. L. d'Arre discovered the mysterious "wandering" star on the very first night. It took scientists three days to finally be convinced of the validity of the calculations of theorists and their observations. Finally, on September 23, 1846, the world was announced the discovery of the eighth planet of the solar system, which was assigned the name proposed by the Russian astronomer, director of the Pulkovo Observatory V.Ya. Struve - Neptune.
By the way, the final question of who is considered the discoverer of the planet has not yet been resolved, but the whole story is a true triumph of celestial mechanics.
Within a month, the first satellite of Neptune was discovered. For almost a century he did not have his own name. In 1880, the French astronomer C. Flammarion proposed to name the satellite Triton, but since it was the only one until 1949, the simple name was more common in scientific circles - the satellite of Neptune. This celestial body, due to some of its features, deserves detailed consideration.
Triton - satellite of Neptune
The championship of the discovery of Triton (10.10.1846) belongs to the British astronomer W. Lassel. The size of this largest satellite of Neptune is similar to the size of the moon, however, in mass it is 3.5 times lighter. This is due to the fact that Triton, presumably, a third consists of ice. The composition of the surface mantle includes frozen nitrogen, methane and water (from 15 to 30%). That is why the reflectivity of the satellite surface is very high and reaches 90% (the same indicator for the Moon is 12%). Despite the possible geological activity, it is almost the coldest object in the solar system with an average temperature of –235 ° .
Not like everyone
A distinctive feature of Triton is that it is the only large satellite known to science with a retrograde rotation (opposite to the rotation of the planet around its own axis). In general, the orbit of Triton is distinguished by unusual characteristics:
- almost perfect circle shape;
- strong inclination to the planes of the ecliptic and equator of the planet itself.
According to modern scientists, the largest satellite of Neptune was "captured" by a planet from the Kuiper Belt during one of the approximations. There is a hypothesis that the mutual tidal forces of a satellite and a planet noticeably heat the latter, and the distance between them is steadily decreasing. Perhaps in the near future (by cosmic standards, of course) a satellite, going beyond the Roche limit, will be torn apart by the planet’s gravitational forces. In this case, a ring is formed around Neptune, which, with its size and magnificence, will eclipse the famous rings of Saturn.
How many moons does Neptune have?
The second satellite of the planet was discovered only in 1949 by the American D. Kuiper. Its name - Nereida - is a small celestial body (diameter about 340 km) received by the name of one of the sea nymphs in ancient Greek myths. The satellite has a very remarkable orbit with the highest eccentricity (0.7512) among the satellites of not only Neptune, but also other planets. The minimum satellite approach distance is 1,100 thousand km, the maximum is about 9,600 thousand km. It is speculated that Nereida was also once captured by the gas giant.
Larissa (another nymph) is the third and last satellite of the planet Neptune, discovered by earth observers in the last century. This happened in 1981, due to some circumstances. Quite by chance, it was possible to fix the star’s coverage with this object. The final answer to the question of how many satellites Neptune gave the Voyager 2 (NASA) interplanetary space probe, which launched to study the far reaches of the solar system. The device reached the vicinity of the planet in 1989 after a twelve-year journey.
Suite of the Underwater Lord
The names of the moons of Neptune, one way or another, are associated with the god of the seas. Today, science knows about 14 objects that revolve around the planet. The Voyager 2 spacecraft also confirmed the existence of six rings, consisting mainly of frozen methane. Five of them have their own names (as they move away from the surface of the planet): Halle, Le Verrier, Lassel, Argo and the Adams ring.
In general, the importance of the information transmitted by Voyager for modern astronomy is difficult to overestimate. Six satellites were discovered, the presence of a weak nitrogen atmosphere on Triton, polar caps and traces of geological activity on its surface. During its operation in the Neptune system, the automatic interplanetary station took more than 9,000 photographs.
Nameless S2004N1, Neso and others
From the list of Neptune's satellites, presented in the table as they are remotely from the planet, one can get brief information about these cosmic bodies.
| room | Title | Opening year | Semi-major axis (thousand km) | Size / Diameter (km) | Period of circulation (days) | Weight (t) |
| 1 | Naiad | 1989 | 48.23 | 96 * 60 * 52 | 0.294 | 1.9 × 10 14 |
| 2 | Thalassa | 1989 | 50.08 | 104 * 100 * 52 | 0.311 | 3.5 × 10 14 |
| 3 | Despina | 1989 | 52.52 | 180 * 148 * 128 | 0.335 | 2.1 × 10 15 |
| 4 | Galatea | 1989 | 61.95 | 204 * 184 * 144 | 0.429 | 2.1 × 10 15 |
| 5 | Larissa | 1981 | 73.55 | 216 * 204 * 168 | 0.555 | 4.9 × 10 15 |
| 6 | S2004N1 | 2013 | 105.30 | 18 | 0.96 | is unknown |
| 7 | Proteus | 1989 | 117.65 | 440 * 416 * 404 | 1,122 | 5.0 × 10 16 |
| eight | Triton | 1846 | 354.8 | 2707 | 5,877 | 2.1 × 10 19 |
| nine | Nereid | 1949 | 5513.4 | 340 | 360.14 | 3.1 × 10 16 |
| ten | Galimeda | 2002 | 15728 | 48 | 1879.71 | 9.0 × 10 13 |
| eleven | Psamafa | 2003 | 46695 | 28 | 9115.9 | 1.5 × 10 13 |
| 12 | Sao | 2002 | 22422 | 44 | 2914.0 | 6.7 × 10 13 |
| 13 | Laomedea | 2002 | 23571 | 42 | 3167.85 | 5.8 × 10 13 |
| fourteen | Not with | 2002 | 48387 | 60 | 9374.0 | 1.7 × 10 14 |
From the information presented, several noteworthy facts can be distinguished. The last satellite discovered in 2013 is the S2004N1 object, which has not yet been given its own name.
Neptune's satellites are usually divided into internal (from Naiad to Proteus) and external (from Triton to Neso). The former are characterized by a dark surface and irregular shape. Despina and Galatea, rotating in the region of the rings, according to experts, are gradually being destroyed and supplying them with “building” material.
External satellites have very elongated orbits. Some parameters suggest that Galimeda is a detached part of Nereida. The distance of almost 49 million km makes it possible to consider Neso the most remote satellite from the planet in the solar system.