Asteroids: the most famous asteroids, their temperature, size and classification. The bulk of asteroids discovered by scientists (about 98%) are located between the planetary orbits of Jupiter and Mars. Their distance from the luminary ranges from 2, 06-4, 30 AU. That is, for periods of circulation, fluctuations have the following range - 2, 9-8, 92 years. In the group of minor planets, there are those that have unique orbits. These asteroids are usually given masculine names. The most popular are the names of the heroes of Greek mythology - Eros, Icarus, Adonis, Hermes. These minor planets move outside the asteroid belt. Their remoteness from the Earth fluctuates, asteroids can approach it at 6 - 23 million km. A unique approach to the Earth took place in 1937. The Minor Planet Hermes approached it by 580 thousand km. This distance is 1.5 times the distance of the Moon from the Earth.
The brightest known asteroid is Vesta (about 6m). A large mass of minor planets has an intense brilliance during the opposition period (7m - 16m).
The calculation of the diameters of asteroids is carried out on the basis of their brightness, ability to reflect visible and infrared rays. Out of 3,5 thousand of the list, only 14 asteroids have a transverse size exceeding 250 km. The rest are much more modest, there are even asteroids with a diameter of 0.7 km. The largest known asteroids - Ceres, Pallas, Vesta and Hygia (1000 to 450 km). Small asteroids do not have a spheroid shape, they are more similar to shapeless boulders.
Asteroid masses also fluctuate. The largest mass is determined for Ceres, it is 4000 times smaller than the size of planet Earth. The mass of all asteroids is also less than the mass of our planet and is one thousandth of it. All minor planets have no atmosphere. Some of them have axial rotation, which is established by regularly recorded brightness changes. So, Pallas has a rotation period of 7, 9 hours, and Icarus turns in only 2 hours and 16 minutes.
According to the reflectivity of asteroids, they were combined into 3 groups - metallic, light and dark. The latter group includes asteroids, the surface of which is capable of reflecting no more than 5% of the incident light of the Sun. Their surface is formed by rocks similar to carbonaceous and black basalt. That is why dark asteroids are called carbonaceous.
The highest reflectivity of light asteroids (10-25%). These celestial bodies have a surface similar to silicon compounds. They are called stone asteroids. Metallic asteroids are the least common. They are similar to light, the surface of these bodies is more reminiscent of alloys of iron and nickel.
The correctness of this classification is confirmed by the chemical composition of meteorites falling to the Earth's surface. An insignificant group of asteroids is distinguished, which cannot be classified according to this criterion. The percentage of the 3 given groups of asteroids is as follows: dark (type C) - 75%, light (type S) - 15% and 10% metallic (type M).
The minimum reflectivity of asteroids is 3-4%, and the maximum reaches 40% of the total amount of incident light. Small asteroids rotate most rapidly, they are very diverse in shape. Presumably they are composed of the material that formed the solar system. This assumption is confirmed by the change in the dominant type of asteroids belonging to the asteroid belt with distance from the Sun. In their motion, asteroids inevitably collide with each other, scattering into small parts.
The pressure inside the asteroids is not great, therefore, they are not warmed up. Their surface may slightly heat up under the influence of sunlight, but this heat is not retained and goes into space. Estimated asteroid surface temperature indicators range from -120 ° C to -100 ° C. A significant increase in temperature, for example, up to +730 ° C (Icarus), can be recorded only at the moments of approaching the Sun. After the removal of the asteroid from it, a sharp cooling occurs.
