Ten satellites of Saturn were observed in telescopes, but the flights of spacecraft brought discoveries: by 1980, 7 new satellites were known. They are so small that they cannot be observed from Earth, but some of them affect the dynamics of Saturn’s system.
The atlas, whose orbit is near the outer edge of ring A, does not allow the particles of the ring to go beyond it.
Titan is the only largest satellite of Saturn, which is compared to the Galilean satellites of Jupiter. Others are much smaller,
Titanium has a radius of 2575 kilometers. The major half-axis of the orbit is equal to 1,222-106 km. The mass of Titan is defined as 0.0225 of the mass of the Earth. The average density is 1.881 g / cm. The period of orbital rotation is 15,945 Earth days. The surface of Titan is shrouded in clouds. The atmosphere of this satellite is dense, like the atmosphere of Venus. Titanium has a greenhouse effect near the surface. The main component of the atmosphereera of Titan – N2, but there is a significant admixture of CH4. The infrared spectrum is dominated by methane.
The temperature of the upper atmosphere is uniform, the temperature on the surface of Titan is 94 K. Interestingly, the surface of this satellite is isothermal throughout the sphere. Aerosols are present in the atmosphere, which are apparently the product of photochemical transformations of methane. Organic molecules are also observed.
Iapetus is the third largest satellite of Saturn. Its radius is 730 km, the major half-axis of the orbit – 3.56 106. The mass of Iapetus is 3.15 ten thousandths of the mass of the Earth. The period of rotation around Saturn is 79,331 Earth days. The hemisphere facing Saturn is covered with craters. Many craters with a dark bottom were found on the light matter of the visible side of Iapetus, and there are no craters with a light bottom or other white spots on the dark matter.
Rhea is slightly larger than Iapetus. its radius is 765 km, its diameter is 1530 km, and its density is 1.24 ± 0.05 g / cm3. Ray is an example of a relatively simple ice satellite. It lacks the dark matter characteristic of Iapetus.
The Moon’s albedo is 0.073, ie it reflects on average only 7.3% of the Sun’s light rays, so the observed surface of our satellite is quite dark. At full moon the moon has a magnitude at an average distance of -12.7. In this phase, it illuminates the Earth 465,000 times weaker than the Sun. The amount of light sent by the Moon varies with the change of phases, but not in direct proportion, but with a factor, so that when the Moon is in a quarter and we see half of its disk light, it sends us not 50% but only 8% of full light. Of the moon.
Ancient astronomers and philosophers already knew that moonlight was only a reflection of sunlight. It has been suggested that the Moon is Earth-like, inhabited by animals and humans. Aristotle considered the surface of the Moon to be a mirror, which explained the visible dark spots: it is only a reflection of the earth’s seas and continents. With the advent of the first European telescopic observations made by Galileo, the countdown to scientific selenography began.
In August 1609, Galileo first observed the lunar mountains. He wrote in the Star Gazette: “We have come to the conclusion that the surface of the moon is neither smooth nor flat, nor perfectly spherical, as a whole legion of philosophers thought of it, but, on the contrary, uneven, rough, speckled with depressions and heights. ” From Galileo there is a tradition to call the dark areas of the moon’s surface seas and oceans.
In 1619, P. Scheiner published a monthly map. its diameter was about 10 cm. In 1647 J. Hevelius published the book “Selenography, or description of the Moon”. In those days, telescopes were bulky and imperfect, long-focusing enough to reduce chromatic aberration. Therefore, the monthly charts were very inaccurate.
In 1651, D. Riccioli drew up a map of the Moon, where more than two hundred parts received their own names. Hevelius called some lunar mountain ranges earthly names – the Apennines, the Alps, the Caucasus, the Carpathians. Riccioli continued the tradition. For “seas” and “oceans” he chose names not related to the earth, but very romantic: Ocean Storm, Sea of Rains, Lake of Dreams, Bay of Rainbows, Swamp of Mists. The craters were named after Galileo, Archimedes, Plato, as well as church figures, who for some reason revered Riccioli.
A detailed map of the Moon was published in 1830-1837. Behr and Medler. 7735 details were marked on it. In 1878, J. Schmidt published an even more detailed map, which for many decades was considered the best. It is marked with 32,856 parts.
The next stage in the cartography of the lunar surface was the first photo atlas, published in 1897 by the Paris Observatory. In 1904, a photo atlas was published in the United States. By the end of the twentieth century, the most popular was Kuiper’s photo atlas (USA, 1960), which contains 280 maps of 44 parts of the Moon, taken in varying degrees of illumination. The images in this atlas show details up to 800 m in size.
In 1959, the reverse side of the moon (USSR) was photographed for the first time, and in 1960, the USSR Academy of Sciences published the first “Atlas of the reverse side of the moon.” It contains a description of about 500 objects.
On modern maps of the Moon, the image is straight, ie the north pole is located at the top of the map, the south – at the bottom. The hemisphere of the Moon, facing the North Star, is called the northern, the opposite – the southern. Selenographic coordinates include latitude and longitude. Selenographic latitude is the angle between the radius drawn from the center of the Moon to a given point on the surface and the plane of the lunar equator. Selenographic longitude is the angle drawn between the plane of the prime meridian and the plane of the meridian of a given point on the lunar surface. The prime meridian passes on the Moon near the crater of Mestin.
Relief of the Moon
The relief of the lunar surface has been studied for about 400 years. During this time, a specific terminology has emerged that can be misleading, because lunar formations have traditionally been named by analogy with terrestrial ones, although they often have nothing in common either in structure or in origin.
The closest to terrestrial forms on the Moon are mountain ranges and mountain ranges. They include both well-preserved and partially destroyed objects, or objects with smoothed shapes. Erosion of the lunar relief occurs due to the influence of a complex of different causes.
Lunar rocks crack and grind under the influence of temperature differences (daily temperature difference is 270 – from +120 to -150). The corpuscular and short-wave radiation of the Sun also has a destructive effect on the surface of the Moon. In addition, it is believed that volcanism was involved in the formation of the lunar relief, which in the past had great power and was accompanied by volcanic eruptions, lava eruptions and various tectonic processes.
A characteristic feature of the lunar relief is a large number of annular mountains. Today they are called lunar craters, but in old printed publications there is another classification. Thus, the circular mountain range that limits the smooth valley is called the circus; Depressions several kilometers in diameter with a flatter bottom are called pores or small craters.
Some areas of the Moon are characterized by chains of craters about hundreds of kilometers long.
In addition to the mountains, the positive (convex) forms of the lunar relief include peaks (fairly isolated peaks on the flat bottom of the lunar seas) and shafts – flat hills about 1-2 km high.
Negative (concave) forms of lunar relief include cracks, furrows and valleys. Cracks are usually large formations tens to hundreds of kilometers long and tens to hundreds of meters deep and wide. The furrows are similar to cracks, but the slopes are less steep and the bottom is flatter. The valleys are characterized by the greatest width and plane of the bottom.
The modern appearance of the Moon has been formed over billions of years, and the evolution of the lunar surface continues today. The following periodization of the evolution of the lunar surface (according to Khabakov) is accepted:The initial period. The moon is covered with a primitive crust with a hilly or crested surface. Ring mountains are absent. The oldest period. Active cratering due to internal processes. Ancient (Altai) period. Lowering of large areas of the lunar cortex and lava eruption. Formation of the oldest seas that have disappeared today. Named after the Altai Range, which may be the shore of the ancient sea. Middle (Ptolemaic) period. Intense cratering and the disappearance of ancient seas. Named after the crater Ptolemy, which probably originated in that era and is one of some of the oldest surviving ring mountains. New (oceanic) period. There were new large-scale lowering of the lunar crust. Most of the craters available at that time are flooded https://123helpme.me/a-tree-grows-in-brooklyn/ with lava. A modern belt of lunar seas with outlines known to us is being formed. The latest (Copernican) period. The appearance of new craters on the surface of the lunar seas. Named after the Copernicus crater, characteristic of this period, with a perfectly preserved sharp relief.
The formation of the moon
The origin of the Moon has naturally interested astronomers since the time of Galileo, who first saw the topography of the lunar surface. There have been many speculations about how the Earth’s satellite was formed.
The most widely developed:the hypothesis of the initial division, the hypothesis of capture, the hypothesis of the simultaneous formation of the Moon and the Earth.
The first theory belongs to the biologist and naturalist J. Darwin, who suggested that initially both planets were a single hot mass. In general, Darwin’s hypothesis was in the stream of competing theories about the cold and hot formation of the planets of the solar system.
According to the first, they were originally a cold gas-dust cloud, which is heated by compression and the release of large amounts of energy, according to the second – were initially heated, but gradually cooled, retaining only a hot core. Darwin leaned towards the second option. In his opinion, as it cools and accelerates rotation, a single hot mass is divided into two unequal parts, the larger formed the Earth, the smaller – the Moon, and the latter was formed from the outer layers of the original mass, which separated …