Hundreds of millions of small objects with ice in the Kuiper belt are considered to be the original stars left over from the early formation of the solar system, as well as the sources of Centauri and Jupiter family comets. Therefore, the study of Kuiper Belt objects is of great scientific significance for understanding the origin and evolution of the solar system, the origin of water and life on earth. On New Year’s day, 2019, NASA’s New Horizons spacecraft flew over the Kuiper belt small object “2014 mu69”. < p > < p > on October 5, the journal Nature astronomy published on-line the research results of the cooperation between Zhao Yuhui, associate researcher of the laboratory of planetary science and deep space exploration, Zijinshan Observatory, Chinese Academy of Sciences, and other institutions, as well as Germany’s Mapu Solar System Research Institute. Researchers have established and used the model of shape evolution caused by the volatilization of active substances of small celestial bodies in the solar system to analyze the peculiar flat shape of “Tianya Haijiao”, and draw a brand-new conclusion: during the period from 1 million to 100 million years after its birth, a large number of active gases such as methane, carbon monoxide and nitrogen volatilized, resulting in its flat shape The formation of the structure, and this “slimming” mechanism may exist widely in the early stage of the formation of small objects in the Kuiper belt. In 1951, Kuiper developed the hypothesis about the origin of short period comets put forward by E. Edgeworth, an Irish astronomer, into the corresponding theory, so later generations called the expected loop Kuiper belt, or Edgeworth Kuiper belt. In 1992, astronomers used optical telescopes to observe an asteroid in the circumsolar orbit outside Neptune orbit, and then found more similar objects. By 2006, the total number of observations has exceeded 1000, the largest of which is 1200 km in diameter, and the rest are mostly 200-400 km in diameter. < / P > < p > now, we can observe countless small objects in the Kuiper belt through ground-based telescopes, or fly over the Kuiper belt like new horizons, and take a close-up picture of those mysterious small objects. Zhao Yuhui told Science and Technology Daily that the Kuiper belt is located outside the disk of the solar system, outside the orbit of Neptune, 30-50 astronomical units (AU, 1 astronomical unit is about 149.6 million km) away from the sun, mainly composed of small celestial bodies or remnants formed by the solar system. Similar to the asteroid belt, it has hundreds of millions of small solid objects, and is the birthplace of Jupiter family comets. But unlike the asteroid belt, most Kuiper Belt objects are mainly composed of frozen volatiles, such as carbon dioxide and water, rather than metallic materials. The most famous object in the Kuiper belt is Pluto, once the ninth planet in the solar system. But then it was excluded because it was about the same size as some small objects in the Kuiper belt. The origin of small objects in the Kuiper belt is still an unsolved mystery at present. Scientists tend to think that small Kuiper Belt objects of different ethnic groups may have formed in different positions in the solar system. 4.5 billion years ago, in the region close to the sun, many interstellar materials revolved around the sun, collided with each other, and formed the solid cores of the earth and other earth like planets, as well as gas giant planets. In regions far away from the sun, such as the Kuiper belt, where the temperature is extremely low, a lot of cosmic dust, ice, and gas are preserved, forming a large number of objects smaller than planets. There are hundreds of millions of small ice bodies in the Kuiper belt, which are considered to be the original stars left over from the early formation of the solar system, and also the source of Centauri and Jupiter family comets. Therefore, the study of objects in the Kuiper belt is of key scientific significance for understanding the origin and evolution of the solar system, the origin of water and life on earth. As the most stable group of small objects in the Kuiper belt, the “ends of the earth” group is the most stable group of small objects in the Kuiper belt, and its orbit is rarely disturbed by the outside world in the evolution process, so it belongs to the local small objects in the region. The exploration of “the ends of the earth” can provide a lot of valuable information for human to study the formation and evolution of solar system and celestial bodies. < / P > < p > “the reason why we call” Tianya Haijiao “as a” cold classic “is not because of its low temperature, but from the point of view of dynamics, this kind of celestial body has a more stable orbit, which can be said to be the most stable type of celestial body in the solar system.” Zhao Yuhui said that in addition to the “cold classical” group, there are “hot” classical Kuiper Belt objects, discrete disk small objects, Neptune resonance orbit small objects and other types of small objects in the Kuiper belt. The end of the earth is an exciting astronomical discovery. It is about 6.6 billion kilometers away from the earth. It is a two-part double lobed object with a surface diameter of no more than 32 kilometers. Its peculiar flat shape is considered to be the most unexpected result obtained by the new horizon probe. And its color is red, the temperature is very low. “This indicates that it contains Torrin, a simple organic compound such as methane and ethane, which is formed by ultraviolet radiation and exists on cold objects far away from stars. The available data show that the maximum surface temperature is about – 218.15 ℃ Zhao Yuhui said. In the Kuiper belt, “Tianya Haijiao” is a very stable “cold classic” group. It can be said that it has not changed much since it was born 4.5 billion years ago. Therefore, “Tianya Haijiao” is likely to retain some materials from the early formation of the solar system. Small objects with < / P > < p > double lobes are common in the solar system. However, flat objects are rare, and there is no relevant theory and model to explain its existence. Before that, the international astronomical community did not give a corresponding explanation for the strange shape of “the ends of the earth”. It was previously speculated that this flat shape was formed during the collapse of nebulae in the early solar system. < p > < p > Zhao Yuhui’s team independently developed a set of model for the shape evolution of small celestial bodies under the volatilization of active substances. Using this model, they carried out relevant research on the Jupiter family comet 67p / CG and other Jupiter family comets. < / P > < p > “although our samples are limited by the observation data, the model has been verified in the study of the north-south asymmetry of comet 67p / CG and the evolution of the surface topography of comet 67p / CG, which shows that our model is reliable.” Zhao Yuhui said. Zhao Yuhui told reporters that although, like its name, “the ends of the earth” is very far away from us, and “new horizon” is only a glance at it, it is still of great significance to study its shape. The research shows that in the early stage of the formation of planets in the solar system, micron sized dust coheres with each other to form millimeter or centimeter sized particles, and these particles continuously gather to form spherical or ellipsoidal stars with the size of tens to hundreds of kilometers. The “ends of the earth” may have been originally formed by the combination of two such stars. In the early stage of the formation of the solar system, the interstellar space is still filled with a large amount of gas and dust, blocking most of the solar radiation. The temperature in the remote Kuiper belt is still very low. A large number of highly active molecules such as methane, carbon monoxide and nitrogen can exist in the stars in the form of solid state. As the gas and dust in the solar system are dispersed, the solar radiation becomes intense and the temperature rises gradually. The active gas on the surface and inside of “Tianyahaijiao” begins to volatilize and the material gradually loses. < / P > < p > because the solar radiation at the ends of the earth is far greater than that at the equatorial region, the volatilization speed of the gas is greatly improved, and the overall shape tends to be flat. < / P > < p > “the shape evolution process is completed in about 1 million to 100 million years after its formation, which is very short compared with its age of 4.5 billion years.” Zhao Yuhui said. According to Zhao Yuhui, this shape evolution mechanism is likely to be prevalent in small objects in the Kuiper belt during the early stage of the formation of the solar system. However, when some small objects move closer to the sun, such as centaur or Jupiter family comets, due to stronger solar radiation, relatively less active gases (such as carbon dioxide and water) volatilize, and then experience a similar shape evolution process. < p > < p > “studies have shown that a large number of active gases such as methane, carbon monoxide and nitrogen exist in the early stage of the formation of the solar system. Understanding their mechanism is of great significance to the study of the formation of early stars in the solar system and the formation and evolution of small celestial bodies in the solar system Zhao Yuhui said. Spontaneous combustion at a Guangzhou Motor vehicle intersection and other traffic lights in Shenzhen