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AstronomySolar system



Neptune is the eighth and most distant planet in the Solar System.
Furthermore, it is, in order of size, the fourth largest planet, considering its diameter, and the third largest if considering its mass.
Neptune has 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, whose mass is equal to 15 Earth masses, but is less dense than Neptune. The name of the planet is dedicated to the Roman god of the sea (Neptune); its symbol is ♆ (Neptune’s astronomical symbol), a stylized version of Neptune’s trident.
This planet was discovered on the evening of September 23, 1846 by Johann Gottfried Galle, with the telescope of the Berlin Astronomical Observatory, and by Heinrich Louis d’Arrest, an astronomy student who assisted him; Furthermore, Neptune was the first planet to have been found through mathematical calculations rather than through regular observations: in fact, unusual changes were periodically observed in the orbit of Uranus, which led astronomers to believe that there was, outside, an unknown planet that it disturbed its orbit. The planet was discovered within just one degree of the predicted location.
The moon Triton was detected shortly thereafter, but none of Neptune’s other thirteen natural satellites were discovered before the 20th century.

Astronomical Observation –
Astronomical observation of Neptune, the outermost planet in our solar system, can be a fascinating experience.
Neptune is located in the outer solar system, besides Uranus, and is a gas giant planet. It is located at an average distance of about 4.5 billion kilometers from the Sun.
To observe Neptune, you need a telescope. Given the considerable distances, a telescope of at least 8 inches aperture is recommended to obtain a satisfactory view. Using color filters can help improve surface detail.
Because of its considerable distance and relatively small size, Neptune will appear as a small bluish disk through a telescope. Therefore, we cannot expect details similar to those observable on Jupiter or Saturn.
Neptune is best observed when it is in opposition, that is, when it is on the other side of the Sun from the Earth. During this time, Neptune is closer and brighter. Oppositions occur approximately every 164.8 Earth days.
You can use sky simulation software or smartphone apps to determine Neptune’s current position in the night sky. This will help you know when and where to look.
Atmospheric conditions greatly influence the quality of observation. Try to observe on clear, haze-free nights to get the best images possible.
If, in addition, you have access to a camera adapted for the telescope, you can try to capture images of Neptune. However, because it is a small, distant planet, obtaining detailed images can be a challenge.
It is also advisable to take advantage of any astronomical events, such as eclipses or transits, involving Neptune. These events can provide unique opportunities for observing and studying the planet.
Remember that observing planets like Neptune requires patience and practice. By investing some time in becoming familiar with your telescope and local sky conditions, you will be able to better appreciate the features of this distant world in our solar system.

Physical characteristics –
Neptune has a similar composition to Uranus, and both have compositions different from those of the larger gas planets Jupiter and Saturn. For this reason they are sometimes classified in a separate category, the so-called “frost giants”. Neptune’s atmosphere, although similar to those of both Jupiter and Saturn in being composed primarily of hydrogen and helium, also has greater proportions of “ices”, such as water, ammonia and methane, along with traces of hydrocarbons and perhaps nitrogen. In contrast, the planet’s interior is essentially composed of ice and rock like its fellow Uranus. The traces of methane present in the outermost layers of the atmosphere contribute to giving the planet Neptune its characteristic intense blue color.
Furthermore, Neptune has the strongest winds of any planet in the Solar System. Gusts at speeds exceeding 2100 km/h were measured. At the time of Voyager 2’s flyby in 1989, the southern hemisphere of the planet had a Great Dark Spot similar to Jupiter’s Great Red Spot; the temperature of Neptune’s highest clouds was about −218 °C, one of the coldest in the Solar System, due to the great distance from the Sun. The temperature at the center of the planet is about 7000 °C, comparable with the surface temperature of the Sun and similar to that of the nucleus of many other known planets. The planet also has a faint ring system, discovered in the 1960s but confirmed only by Voyager 2.
Neptune is the fourth largest planet in the solar system by diameter and the third by mass. Its equatorial diameter is approximately 49,528 kilometers.
Its atmosphere is mainly composed of hydrogen (about 80%) and helium (about 19%). It also contains traces of methane, ammonia, water vapor and other compounds.
Neptune has a deep blue color, which is the result of the presence of methane in its atmosphere. Methane absorbs red light, leaving the blue color to predominate.
Neptune, as mentioned, is known for its intense atmospheric storms. The most famous is the Great Dark Spot, an ancient storm that has been observed since the passage of the Voyager 2 probe in 1989.
Neptune has rings, although they are very faint and not as spectacular as those of Saturn. Its rings are composed mainly of dust and ice particles.
The planet has a powerful magnetic field, which is about 27 times stronger than Earth’s. However, Neptune’s magnetic field is tilted relative to its rotation axis by about 47 degrees.
Neptune’s rotation period is approximately 16 hours. However, the length of a day on Neptune is approximately 16.1 hours due to its motion of revolution around the Sun.
This planet has several natural satellites, including Triton, the largest of them. Triton is known to be unique in the solar system as it orbits the planet in the opposite direction to Neptune’s rotation itself, suggesting that it may have been captured by the planet’s gravity at a later time.

Space missions –
The planet has only been visited by one space probe, Voyager 2, which passed by it on August 25, 1989.
Voyager 2 was one of the first to explore the outer solar system, launched by NASA on August 20, 1977 and still active as of 2023. It was launched from Cape Canaveral, aboard a Titan III rocket a few days before its twin Voyager 1, also belonging to the Voyager program. The orbit into which the probe was placed led it to graze the two giant planets, Jupiter and Saturn. During the journey, the technicians realized that they could exploit a rather rare planetary alignment to continue the probe towards the icy giants, Uranus and Neptune. Most of the information we have about these two planets comes from Voyager 2.

Guido Bissanti

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