Asteroids, or small planets, are much inferior totheir dimensions to such bodies of the solar system as the Earth, Venus and even Mercury. However, they can not be considered as full-fledged "inhabitants" of our piece of the Galaxy.
The asteroids of the solar system are concentrated inseveral zones. The most impressive part of them is placed between the orbits of Mars and Jupiter. This cluster of small bodies was called the Main Belt of Asteroids. The mass of all objects located here by space standards is negligible: it is only 4% of the lunar mass. And the main contribution to this parameter is made by the largest asteroids. And their movement, and the movement of their smaller counterparts, as well as parameters such as composition, shape and origin, attracted the attention of astronomers as early as the beginning of the XIX century: Ceres, previously considered the largest asteroid, and now referred to the number of dwarf planets, was discovered the first of January 1801.
The Kuiper Belt, the Orta cloud and the scattered steel diskConsider and study as places of accumulation of a large number of small celestial bodies a little later. The first of these is located beyond the orbit of Neptune. It was opened only in 1992. According to researchers, the Kuiper belt is much longer and more massive than the similar formation between Mars and Jupiter. The small bodies located here differ from the objects of the Main Belt with the composition: methane, ammonia and water prevail over the hard rocks and metals characteristic of the "residents" of the Asteroid Belt.
The existence of the Orta cloud is not proven today,However, this hypothesis corresponds to many theories describing the solar system. Presumably, the Orta cloud, which is a spherical region, is located behind the orbits of the planets, at a distance of about a light year from the Sun. Here are the space objects, consisting of ammonia, methane and water ice.
The area of the scattered disk overlaps somewhat with the Kuiper belt. Scientists do not yet know its origin. There are also objects that consist of different types of ice.
For an accurate understanding of the subject matter, it is necessaryto divide two astronomical concepts: "comet" and "asteroid". Until 2006, there was no certainty about the differences between these objects. At the General Assembly of the IAU in the named year, the comet and the asteroid were fixed with specific signs allowing more or less confidently to attribute each cosmic body to a certain category.
A comet is an object moving along a veryelongated orbit. When approaching the Sun as a result of the sublimation of ice located near the surface, the comet forms a cloud of dust and gas to someone - a cloud that grows as the distance between the object and the light decreases and is often accompanied by the formation of a "tail".
Asteroids of a coma do not form and, as a rule, haveless elongated orbits. Those of them that move along trajectories similar to comets are considered to be the nuclei of so-called extinct comets (an extinct or degenerate comet is called objects that have lost all volatile substances and do not therefore form coma).
Really big by space standardsobjects in the main belt of asteroids are very few. Most of the mass of all bodies located between Jupiter and Mars falls on four objects - Ceres, Vesta, Pallada and Gigeia. The first until 2006 was considered the largest asteroid, then it was given the status of a dwarf planet. Ceres is practically a round body with a diameter of about 1000 km. Its mass is approximately 32% of the total mass of all known objects of the belt.
The most massive object after Ceres is theVesta. By the size of the asteroids it is only ahead of Pallas (after the recognition of Ceres by a dwarf planet). Pallas differ from the others and an unusually strong inclination of the axis.
Gigeya - the fourth largest in size and mass objectThe main belt. Despite its size, it was discovered much later than several smaller asteroids. This is due to the fact that Gigeya is a very dull object.
All the named bodies revolve around the Sun in the same direction as the planets, and do not cross the trajectory of the Earth's motion.
The largest asteroids and their motion obeyThe same laws as the movement of other similar bodies of the belt. Their orbits are constantly affected by the planets, especially the tangible influence of the giant Jupiter.
For weakly eccentric orbits, allasteroids. The motion of asteroids, which is subjected to the action of Jupiter, passes through several shifting orbits. These displacements can be described as oscillations around a certain average position. For each such oscillation, an asteroid spends up to several hundred years, so the data of observations to date is not enough to refine and verify the theoretical constructions. However, on the whole, the hypothesis of changing orbits is generally accepted.
The result of the displacement of the orbits is the increasing possibility of collisions. In 2011, data were obtained suggesting that Ceres and Vesta might be encountered in the future.
The largest asteroids and their motion constantlyare under the close attention of scientists. The features of changing their orbits and other characteristics shed light on some cosmic patterns that, in the process of data analysis, are often extrapolated to objects larger than asteroids. The motion of asteroids is studied at the same time and with the help of spacecraft, which temporarily become satellites of certain objects. One of them March 6, 2015 entered the orbit of Ceres.
