What is the Kuiper Belt?

The full name is edgeworth-kuiperbelt (English: edgeworth-kuiperbelt; EKB, usually called Kuiper Belt, or translated as Cooper Belt, Cooper Belt, etc. )

The Kuiper Belt is located at the end of the solar system, and its name comes from the Dutch-American astronomer Kuiper. As early as 1950s, Kuiper and edgeworth predicted that the edge of the solar system outside Neptune's orbit was full of tiny frozen objects, which were the remnants of the primitive solar nebula and the source of short-period comets.

1992, the first kuiper belt object (kbo) was discovered; Today, about 1000 Kuiper Belt objects with diameters ranging from several kilometers to several thousand kilometers have been discovered. Many astronomers believe that Pluto should be excluded from the planets in the solar system and listed as an asteroid in the Kuiper Belt because it is similar in size to an asteroid in the Kuiper Belt. Pluto's satellite should be regarded as its companion. However, since Pluto was discovered before the emergence of the Kuiper Belt theory, it is still traditionally regarded as a planet. In any case, the existence of the Kuiper Belt is now an acknowledged fact, but various questions such as why the Kuiper Belt exists have become part of many unsolved mysteries in the theory of solar system formation.

At a distance of 40 ~ 50 astronomical units from the sun, the orbit with a small inclination was once considered as a void and the end of the solar system. But in fact, there are frozen objects everywhere, large and small, which is very lively, and that is the Kuiper Belt. The Kuiper Belt is the boundary of the solar system as we know it at present, and it is the source of most comets in the solar system. How are these objects on the Kuiper Belt formed? According to the accretion theory of planetary formation, they collide and attract each other in the process of orbiting the sun, and finally attach to celestial bodies of different sizes, forming what they are now.

But this theory has a fatal problem! If a celestial body with a diameter of thousands of kilometers is to be formed in the present position of the Kuiper Belt, the total mass of celestial bodies in the Kuiper Belt should be at least 10 times the mass of the earth. However, it is estimated that the total mass of the Kuiper Belt is only one tenth of that of the Earth. Does the other 99% mass disappear out of thin air?

In order to solve this mystery, several theories have appeared in recent years, but unfortunately they all have some obvious limitations. Now, Professor Harold Levison of SwRI (Southwest Research Institute) and Professor Alessandro Morbidelli of Delacorte Blue Observatory have put forward a theory that objects in the Kuiper Belt are formed closer to the sun and then thrown out by Neptune one by one, thus avoiding the problem of insufficient total mass of the Kuiper Belt.

Twenty years ago, scientists knew that the orbits of planets would drift, especially Uranus and Neptune, which have gradually moved outward since their formation. The theoretical model proposed by Levison and Morbidelli holds that the primitive nebula of the solar system has a previously unknown boundary, which is probably the current position of Neptune, that is, about 30 astronomical units away from the sun. In this range, all planets, satellites, asteroids, comets and celestial bodies in the Kuiper Belt now have enough mass to collide and accrete. Outside this range, there is empty space. When these large celestial bodies formed and gradually moved outward, the celestial bodies on the Kuiper Belt also moved outward. Then when Neptune hit the boundary of the primitive nebula in the solar system, it had to stop and stay in its current orbit. As for these celestial bodies in the Kuiper Belt, they were gradually thrown out in the final stage of Neptune's migration.

The General Assembly of the International Astronomical Union voted to adopt resolution 5, partially adopting the new planetary standard. Pluto was excluded from the list of planets and listed as a "dwarf planet". Since then, the nine planets have become history. Although the textbook has been printed unchanged, it has become the "eight planets" in science.

The 26th General Assembly of the International Astronomical Union has just adopted a new definition of planet. According to the resolution, after Pluto was "delisted" from the nine planets in the solar system, it is suggested that its Chinese translation be changed to ghost star to reflect the meaning that Pluto is a dwarf planet lower than Uranus and Neptune, but the same as Ceres and Andromeda.

Compared with Ceres discovered more than 200 years ago and Ka Rong discovered nearly 30 years ago, Gina is a complete stranger. The serial number of UB 3 13 in 2003 indicates that scientists found that its observation data were obtained in 2003.

A Qin's orbit is a very flat ellipse. It takes 560 years to complete a revolution. The nearest distance from the sun is 38 astronomical units (1 astronomical unit is the distance from the earth to the sun, about 1 100 million kilometers), and the farthest is 97 astronomical units. Because Gina is so far away, the best picture taken by Hubble telescope can only show a white point with extremely low resolution.

Astronomers currently believe that Gina is about 2,300 km to 2,500 km in diameter, only slightly larger than Pluto. Scientists say that Gina's atmosphere may be composed of methane and nitrogen. Now it is too far away from the sun, and the atmosphere has turned into ice. When it moves to perihelion, the surface temperature will rise, and methane and nitrogen will become gaseous again. As for its internal structure, we can only guess that it may be a mixture of ice and rocks, similar to Pluto.

Gina has a satellite, which scientists temporarily call Gabriel. He is an attendant of the belligerent Princess Gina. These informal names will eventually be replaced by formal names.