Uranus and Neptune are twins, distant giant planets, located on the periphery of the solar system. Both planets are very difficult to observe: because of the remoteness of the angular diameters of their disks do not exceed 4". It is almost impossible to distinguish any details on such small disk from the Earth." Voyager-2 has approached Uranus on January 24, 1986, and has carried out the planned program of researches of a planet, its satellites, and rings.
Discovered by W. Herschel in 1781, Uranus is one of the most distant planets. Radio signals from Voyager went from it to Earth for 2 hours and 40 minutes. Because of the strong absorption in the red part of the spectrum, the planet has a green-blue color. Absorption is caused by methane bands, which are present in small amounts in the atmosphere. It is very difficult to distinguish between details on a small disk. The history of Uranus observations is full of contradictory results. Sometimes observers have reported weak bands like Saturn's zones and belts, but have often found no detail. There are reports that the details have appeared and disappeared within a few months.
There have been attempts to link the visibility of details to very long term seasonal changes in Uranus. Its equator plane is tilted to the orbital plane by 82˚ (taking into account the inverse direction of the planet's rotation, this angle is recorded as 98˚). This position of the polar axis leads to many features of the planet. Uranus rotates "lying on its side" as they say. You have to count the inclination as 90˚ so that when you look at the pole whose inclination is indicated, the direction of rotation of Uranus is the same as that of other planets - counterclockwise (for the same reason, the inclination of the Venus axis of rotation is indicated as 177˚). Previously, the Uranus pole, corresponding to this "correct" direction of rotation, was called the north pole. But since it faces the southern hemisphere of the ecliptic, it was renamed to the southern hemisphere by the decision of the MAC (the principle of rotation direction was sacrificed). In 1985, this southern pole of Uranus turned to the Sun and Earth; in those years, we saw Uranus rotating counterclockwise. In the 1990s, the Sun was illuminating the middle southern latitudes of the planet. In 2007, the equatorial region of Uranus turned to the Sun and the Earth, so that in the next 20 years the northern pole will gradually turn towards the Sun, and the visible rotation of the planet from the Earth will be clockwise.
The "lying" position of the axis of rotation conducts to the maximum possible seasonal changes of illumination. During the orbital period of 84 years, the polar day and night last 14 years at 30° latitude, 28 years at 60° latitude and 42 years at the poles. However, only one dependency has been established for the time being from seasonal effects (if they are really seasonal): over the 20 years during which the center of the planet's visible disk shifted from the equator to the pole, the radio-brightness temperature of the visible hemisphere has doubled, from 140 to 290 K.
The well-known history of the discovery of Neptune in 1846: following the calculations of Urbain Leverrier, he was discovered by Johann Gottfried Galle and Heinrich Louis d'Arret. But there is evidence that he has been seen before. In the 234 years before the actual discovery of Neptune, Galileo noticed it, observing the satellites of Jupiter and fixing their position relative to the stars. On December 28, 1612, he again compared their position and wrote in his diary: "The fixed star is followed by another one, along the straight line ... which was observed last night, but then they were further apart from each other. Only 366 years later, when modern researchers were interested in what Galileo saw, it turned out that one of the "stars" was Neptune. Another historical record dates back to 1670 when John Flemstide mapped Neptune as a star.
In August 1989, the U.S. Voyager 2 went out to Neptune and conducted a large observation program. Its rapprochement with the planet turned into a celebration of space exploration. Essentially, Voyager's mission led to a complete update on the entire family of giant planets. For the flight time, the spacecraft transmitted a total of 115 thousand television images, including 9 thousand - in approaching Neptune.