Of the four ringed planets, Saturn's rings are the most spectacular and wonderful. The first discovery of Saturn's rings in history was made by Italian astronomer Galileo. 16 10, Galileo observed Saturn with his newly invented astronomical telescope and found something on its side. Unfortunately, he didn't know what those things were until he died.
1655, Dutch astronomer huygens finally figured out the reason why the shape of Saturn's ring keeps changing: it is because it faces us from different angles. When we just look at it from the side, the thin halo seems to disappear. Saturn's rings are about 10 km thick and 6.6 km wide. It can be subdivided into several rings with dark gaps in the middle.
On March 1977 and 10, astronomers from many countries, including China, observed a rare astronomical phenomenon-Uranus blocking the stars. The observation results surprised scientists: before Uranus covered the star, people had observed a set of "masks", and after Uranus covered the star, another similar set of "masks" was observed. What caused these masks turned out to be some "auras" around Uranus. These rings are extremely thin and far from each other. 1986 65438+ 10 In October, when the American Voyager 2 spacecraft flew over Uranus, it found several new rings. It is now known that Uranus has 1 1 rings.
Voyager 1 launched on1September 1977. 1At the beginning of March, 979, it passed this huge planet from about 275,000 kilometers away from Jupiter and found that Jupiter also had a group of thin rings. Jupiter's ring is about 30 kilometers thick and has a total width of over 6,000 kilometers. The distance between the ring and Jupiter is about 6.5438+0.28 million kilometers.
1989 In August, when Voyager 2 flew over Neptune, it was confirmed that Neptune also had a halo. Neptune has five rings.
It is not clear whether Pluto also has a halo, but some scientists speculate that it should also have a halo.
After observation and research, scientists found that the halo of the planet is mainly composed of countless small fragments. The size of the fragments can be measured in meters. Each debris seems to be a small satellite, orbiting the main planet in its own orbit.
So, how are the rings of these planets formed?
As early as 1850, the French mathematician Roche came to the conclusion that the tidal force generated by planetary gravity can disintegrate planets or passing celestial bodies. This kind of tidal force can prevent the matter moving near the planet from combining into a larger celestial body. The known planetary ring is within this theoretical range, and its boundary is called roche limit, which is a region with stable gravity. Accordingly, scientists have put forward three kinds of speculations about the origin of planetary rings; First, because the satellite entered the roche limit of the planet and was disintegrated by the tidal force of the planet; Second, one or more large stars located in roche limit were smashed into pieces by meteors, forming halo; Thirdly, some primitive materials left over from the early evolution of the solar system could not condense into satellites because they revolved around the sun in the roche limit, and eventually formed halo.
However, scientists can only speculate on the cause of the halo at present. What puzzles them even more is the existence of those narrow rings, because according to the convention, celestial collision, atmospheric resistance and solar radiation will destroy the narrow rings and make them dissipate in space. What protects the narrow ring and makes it exist? Some scholars have suggested that there must be some small satellites on the edge of the narrow ring that have not been observed by people, and their gravity makes the narrow ring form and be protected. This view was confirmed by people's later discovery, because people found two small companion stars not only in Saturn but also in Uranus' narrow ring, and their complex motion interaction made the material movement in the ring lack regularity, which may be the reason why different planetary rings have different shapes.
With the deepening of research, people's initial speculation that the planetary ring is formed by some substances left over from the early evolution of the solar system revolving around the planet has been doubted by more and more scholars. For example, an astrophysicist in Germany believes that 1 100 million years ago, a small comet collided with a Saturn satellite with a diameter of 60 miles, thus forming Saturn's rings.
At the same time, an interesting question is raised: Why do Saturn, Jupiter, Uranus and Neptune have rings, while Mercury, Venus, Mars and Earth have no rings?
Scientists are still putting forward new speculations and hypotheses about the magical planetary rings. However, with the increase of new discoveries in astronomy, planetary rings become more mysterious.