The mysterious and distant Neptune has been known to astronomers for over one hundred and seventy years. His discovery was a triumph of theoretical science. Despite the development of instrumental astronomy and unmanned astronautics, the planet keeps many secrets, and the unusual orbit of Neptune's satellite Triton is still the subject of discussion and hypotheses.
Janus? Neptune
Initially, the eighth planet of the solar system wanted to give the name of the ancient Roman god of the 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 boundless outer space. And there were indeed several scientists who discovered the planet.
It all started with the fact that in 1834, a priest from England, insanely passionate about astronomy, T. D. Hussey, was very surprised, observing the recently discovered planet Uranus, that its true trajectory in the celestial sphere did not coincide with the calculated one. The Holy Father suggested that this deviation is caused by the influence of a massive space object located beyond the orbit of a gas giant.
Who is the discoverer?
British scientist D. K. Adams and Frenchman W. J. Le Verrier independently calculated the approximate position of an unknown body. According to the indicated coordinates, the German astronomer J. G. Halle (Berlin Observatory) and his assistant G. L. d'Arre discovered a mysterious "wandering" star on the very first night. It took scientists three days to finally make sure that the theoreticians' calculations and their observations were correct. Finally, on September 23, 1846, the discovery of the eighth planet of the solar system was announced to the world, 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 K. Flammarion suggested calling 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 is a moon of Neptune
The primacy of the discovery of Triton (1846-10-10) belongs to the British astronomer W. Lassell. The dimensions of this largest satellite of Neptune are similar to the dimensions of the Moon, however, in terms of mass it is 3.5 timeseasier. 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, this is perhaps the coldest object in the solar system with an average temperature of -235 ° C.
Not like everyone else
A distinctive feature of Triton is that it is the only large satellite known to science with retrograde rotation (the opposite of the rotation of the planet around its own axis). In general, Triton's orbit is distinguished by unusual characteristics:
- almost perfect circle shape;
- strong inclination to the planes of the ecliptic and the 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 approaches. There is a hypothesis that the mutual tidal forces of the satellite and the planet noticeably heat up the latter, and the distance between them is steadily decreasing. Perhaps in the near future (by space standards, of course), the satellite, having entered the Roche limit, will be torn apart by the gravitational forces of the planet. In this case, a ring is formed around Neptune, which, with its size and splendor, will outshine the famous rings of Saturn.
How many moons does Neptune have?
The second satellite of the planet was discovered only in 1949year by the American D. Kuiper. Its name - Nereid - this small celestial body (diameter about 340 km) was named after one of the sea nymphs in ancient Greek myths. The satellite has a very remarkable orbit, which has the largest eccentricity (0.7512) among the satellites not only of Neptune, but also of other planets. The minimum satellite approach distance is 1,100 thousand km, the maximum distance is about 9,600 thousand km. There are suggestions that Nereid was also once captured by the gas giant.
Larissa (another nymph) is the third and last satellite of the planet Neptune, discovered by earthly observers in the last century. It happened in 1981, thanks to some circumstances. Quite by accident, it was possible to fix the coverage of a star by this object. The final answer to the question of how many satellites Neptune has was given by the interplanetary space probe Voyager 2 (NASA), launched to explore the far reaches of the solar system. The device reached the outskirts of the planet in 1989 after a twelve-year journey.
Retinue of the underwater lord
The names of the satellites of Neptune, one way or another, are associated with the god of the seas. To date, science is aware of 14 objects circling the planet. The Voyager 2 spacecraft also confirmed the existence of six rings, composed mainly of frozen methane. Five of them have their own names (as they move away from the surface of the planet): Galle, Le Verrier, Lassel, Argo and the Adams ring.
In general, the meaning of the information transmitted by Voyager formodern 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 work in the Neptune system, the automatic interplanetary station took more than 9,000 photographs.
Un titled S2004N1, Neso and others
From the list of Neptune's satellites, presented in the table in order of distance from the planet, you can get brief information about these cosmic bodies.
| Number | Name | Opening year | Major axis (thousand km) | Size/Diameter (km) | Circulation period (days) | Mass (t) |
| 1 | Naiad | 1989 | 48, 23 | 966052 | 0, 294 | 1, 9×1014 |
| 2 | Thalassa | 1989 | 50, 08 | 10410052 | 0, 311 | 3.5×1014 |
| 3 | Despina | 1989 | 52, 52 | 180148128 | 0, 335 | 2.1×1015 |
| 4 | Galatea | 1989 | 61, 95 | 204184144 | 0, 429 | 2.1×1015 |
| 5 | Larissa | 1981 | 73, 55 | 216204168 | 0, 555 | 4, 9×1015 |
| 6 | S2004N1 | 2013 | 105, 30 | 18 | 0, 96 | unknown |
| 7 | Proteus | 1989 | 117, 65 | 440416404 | 1, 122 | 5, 0×1016 |
| 8 | Triton | 1846 | 354, 8 | 2707 | 5, 877 | 2.1×1019 |
| 9 | Nereid | 1949 | 5513, 4 | 340 | 360, 14 | 3, 1×1016 |
| 10 | Galimede | 2002 | 15728 | 48 | 1879, 71 | 9, 0×1013 |
| 11 | Psamatha | 2003 | 46695 | 28 | 9115, 9 | 1, 5×1013 |
| 12 | Sao | 2002 | 22422 | 44 | 2914, 0 | 6, 7×1013 |
| 13 | Laomedea | 2002 | 23571 | 42 | 3167, 85 | 5, 8×1013 |
| 14 | Neso | 2002 | 48387 | 60 | 9374, 0 | 1.7×1014 |
From the information presented, several remarkable facts can be distinguished. The last satellite discovered in 2013 is the object S2004N1, 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, revolving around the rings, according to experts, are gradually being destroyed and supplying them with "building" material.
The outer satellites have very elongated orbits. Some parameters suggest that Galimede is a detached part of the Nereid. The distance of almost 49 million km makes it possible to consider Neso the most distant satellite in the solar system from its planet.
