Uranus and Neptune
Uranus is the seventh planet from the Sun in the solar system. In diameter, it is almost four times larger than the Earth. Very far from the Sun and relatively poorly lit. Uranus was discovered by the English scientist W. Herschel in 1781. It is not possible to distinguish any details on the surface of Uranus due to the small angular dimensions of the planet in the field of view of the telescope. This complicates his research, including the study of the laws of rotation. Apparently, Uranus (unlike all other planets) rotates around its axis as if lying on its side. Such an inclination of the equator creates unusual lighting conditions: at the poles in a certain season, the sun’s rays fall almost vertically, and the polar day and polar night cover (alternately) the entire surface of the planet, except for a narrow strip along the equator. Since Uranus orbits around the Sun for 84 years, the polar day at the poles lasts 42 years, then is replaced by a polar night of the same duration. Only in the equatorial belt of Uranus does the Sun regularly rise and set with a periodicity of uniform axial rotation of the planet. Even in those areas where the sun is located in
Zenith, the temperature on Uranus (more precisely on the visible surface of the clouds) is about -215 ° C. Under such conditions, some gases freeze. According to spectroscopic observations, hydrogen and a small admixture of methane were found in the composition of the atmosphere of Uranus. In a relatively large amount, there is, by indirect evidence, helium. Like other giant planets, Uranus has such a composition, probably almost to the very center. However, the average density of Uranus (1.58 g / cm3) is slightly higher than the density of Saturn and Jupiter, although the matter in the bowels of these giants is compressed much more strongly than on Uranus. This density of Uranus can be explained by the assumption of an increased helium content or the existence of a core of heavy elements in the bowels of Uranus.
One unusual feature of Uranus is discovered in 1977. girdle ring system. They are composed of many separate opaque and, apparently, very dark particles. Unlike Saturn’s rings, the rings of Uranus are narrow, as it were, “filamentous” formations. They are not visible in reflected light and are detected only by a strong weakening of the brilliance of stars, which turned out to be behind the rings for the earth observer during the orbital motion of the planet. The distance of the rings from the center of Uranus is from 1.6 to 1.85 of the radius of the planet.
The satellites of Uranus – Miranda, Ariel, Umbriel, Titania and Oberlon rotate in orbits, the planes of which practically coincide with each other. The whole system as a whole is characterized by an unusual slope – its plane is almost perpendicular to the middle plane of all planetary orbits.
Neptune is the eighth planet of the solar system. Neptune was discovered in an unusual way. It was noticed that Uranus does not move exactly as it is supposed to move under the influence of the Sun and the planets known at that time. Then they suspected the existence of another massive planet and tried to calculate its position in the sky. This extremely difficult task was independently solved independently by the English astronomer J. Adams and the Frenchman W. Le Verrier. Having received the data from Le Verrier, an assistant to the Berlin Observatory I. Halle on September 23, 1846 discovered a planet. The discovery of Neptune was of great importance primarily because it served as a brilliant confirmation of the law of gravity, which is the basis of the calculations. The average distance of Neptune from the Sun is 30.1 AU, the period of orbit rotation is 164 years and 288 days. Thus, from the moment of discovery, Neptune has not even completed a full revolution in its orbit. The apparent angular diameter of Neptune is about 2 “. When measuring such a small diameter with goniometric devices from the surface of the Earth, the relative error is very large. Neptune was able to clarify the diameter on April 7, 1967, when the planet in its movement against the background of the starry sky obscured one of the distant stars. By According to the results of observations from several astronomical observatories, the equatorial diameter of Neptune is 50,200 km. New information on the diameter made it possible to clarify the average density of Neptune: it turned out to be 2.30 g / cm3. These characteristics are typical of giant planets, consisting mainly of hydrogen and helium mixed with compounds of other chemical elements.In the center of Neptune, according to calculations, there is a heavy core of silicates, metals and other elements that make up the Earth’s group. the star during its eclipse by the atmosphere of Neptune gave a lot of additional information, in particular, the average molecular weight of the over-cloud layers of the atmosphere of Neptune was found. It corresponds to molecular hydrogen with a small admixture of methane. Details on the surface of Neptune are very difficult to distinguish. Therefore, the parameters of daily rotation — the position of the axis, direction, and period of rotation — are very difficult to determine from ground-based observations.
. Neptune has only two satellites. The first Triton, discovered in 1846, two weeks after the discovery of Neptune itself. It is larger than the moon in size and mass.