The Asteroid belt is a dense asteroid area in the solar system between Mars and Jupiter orbits. It is calculated from the 120,437 asteroids that have been numbered, and 98.5% of asteroids have been discovered here. The current asteroid belt contains two main types of asteroids: C-type asteroids rich in carbon values ​​and S-type asteroids containing silicon.

The Asteroidbelt is a dense asteroid area in the solar system between Mars and Jupiter orbits. According to statistics from 120,437 asteroids that have been numbered, 98.5% of asteroids were found here. Since this is the densest area of ​​asteroids, it is estimated that there are as many as 500,000, this area is therefore called the main belt, usually called the asteroid belt. In the space area about 2.17-3.64 astronomical units away from the sun, about 500,000 asteroids have gathered, forming an asteroid belt. So many asteroids can be condensed.

Dense asteroid belts

In the asteroid belt, in addition to the universal gravity of the sun, Jupiter's universal gravity plays a greater role.

The asteroid belt is formed by a group of star subs (predecessors of planets that are smaller than planets) in the primitive solar nebula. However, due to the influence of Jupiter's gravity, these stars hinder the formation of planets, causing many stars to collide with each other and form many wreckage and debris. The three largest asteroids in the asteroid belt are Zhishen, Huishen and Vesta, with an average diameter of more than 400 kilometers; there is only one dwarf planet in the main belt - Ceres, with a diameter of about 950 kilometers.

The remaining asteroids are smaller, some even the size of dust. The asteroid belt is very thin, and several spacecraft have passed safely without accidents. Asteroids in the main belt are divided into three categories according to their spectrum and main forms: carbonaceous, silicates and metals. In addition, collisions between asteroids may form a family of asteroids with similar orbital characteristics and colors, and these collisions are also the main source of dust that produces ecliptic light.

In 1766, German astronomer J. Titius accidentally discovered a sequence: (n+4)/10, substituting n=0, 3, 6, 12,... can give a fairly accurate view of the actual distance between each large planet and the sun. This incident did not attract people's attention at first, and later, the director of the Berlin Observatory, J. Bode published it after learning about it, which is known to the astronomical community. After Uranus was discovered in 1781, it was further confirmed that the formula was valid. Bode proposed that there might be another planet between the orbits of Mars and Jupiter.

In 1801, Sicily and G.Plazzi accidentally discovered a small celestial body at 2.77 AU during routine astronomical observations, namely Ceres.

In 1802, astronomer H. Olbere discovered another asteroid in the same region, and then named it Pallas. William Herschel suggested that these celestial bodies were remnants of a planet after it was destroyed. By 1807, the third celestial stars and the fourth veterinary stars were added in the same region. Since these celestial bodies looked similar to stars, William Herschel named asteroid using the Greek root asteroid (satellite) and translated as asteroid in Chinese.

The Napoleonic War ended the first phase of the discovery of the asteroid belt, and the fifth asteroid, Yishen, was not discovered until 1845. Immediately afterwards, the speed of discovery of new asteroids increased rapidly. By mid-1868, there were 100 asteroids discovered. In 1891, Max Wolf introduced astrophotography, which accelerated the discovery of asteroids. In 1923, the number of asteroids was 1,000, 10,000 in 1951, and 100,000 in 1982. Modern asteroid patrol systems use automation equipment to continuously increase the number of asteroids.

Calculation confirmation

After the discovery of the asteroid belt, their orbital elements must be calculated. In 1866, Daniel Kirkwood announced that from the sun, there are blank areas without asteroids at certain distances, and the orbital periods revolving around the sun in these areas have a simple integer ratio to the orbital periods of Jupiter. Kirkwood believes that Jupiter's perturbation caused the asteroid to be removed from these orbits.

In 1918, Japanese astronomer Kiyoji Hirayama noticed that the orbits of some asteroids in the asteroid belt had similar parameters, thus forming a family of asteroids. By the 1970s, a classification system was developed to observe the colors of asteroids. The three most common types were C-type (carbonaceous), S-type (silicate) and M-type (metal). In 2006, astronomers announced that the population of comets was discovered in the asteroid belt, and it was speculated that these comets might be the source of water in the Earth's ocean.

In the early stages of the formation of the solar system, due to the common collision of the accretion process, small particles gradually accumulate to form larger clusters. Once they accumulate enough mass (the so-called MSI), they can attract the surrounding matter with gravity. These stars can steadily accumulate mass into rocky planets or huge

Asteroid Ida and its satellite, Galileo probe shot

I don't know when the mystery of the formation of gas planets and asteroid belts will be solved. However, more and more astronomers believe that asteroids record information about the early stages of the formation of planets in the solar system. Therefore, the origin of asteroids is an important and inseparable link in the study of the origin of the solar system.

Regarding the reason for the formation, a common view is that in the early stages of the formation of the solar system, for some reason, a large planet was not accumulated in this gap between Mars and Jupiter, leaving behind a large number of asteroids.

The currently recognized theory of planet formation is the solar nebula hypothesis, which believes that the materials, dust and gases that constitute the sun and planets in the nebula form a rotating disc due to gravity shrinkage. In the first few million years of the solar system, collisions during the accretion process became viscous, causing small particles to gradually accumulate to form larger clusters, and the size of the particles to stabilize and continue to increase. Once sufficient mass - the so-called MSI - can attract adjacent matter through gravity. These starsons can stably accumulate mass into rocky planets or huge gas planets.

In areas where the average velocity is too high, collision will cause the starson to shatter, inhibit the accumulation of mass, and prevent the generation of celestial bodies of the planet. In areas where the orbital period of the starson is a simple integer ratio to the period of Jupiter, orbital resonance will occur, and the orbits of these starsons will change due to disturbance. In the space between Mars and Jupiter, there are many places where there are strong orbital resonances with Jupiter. When Jupiter moves inward during the formation process, these resonant orbits will also sweep through the asteroid belt, dynamically stimulate the scattered starsons, and increase their relative velocities. Stars are too perturbed in this area (continued until now) and cannot become planets. They can only continue to orbit the sun as before, and the asteroid belt can be regarded as residues of the original solar system.

The earliest explanation for the cause was the explosion theory, which was the tenth largest planet in the solar system, which was decomposed into tens of millions of asteroids.

Asteroid Mathilde, near-Earth asteroid probe shot
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