What are asteroids and what is known about them?

What are asteroids? First of all I would like to say that so-called rocky solids, which move around the solar orbits elliptical shape like planets. However, space asteroids have much smaller dimensions than, in fact, the planets themselves. Their diameter is roughly in the following range: from a few tens of meters to thousands of kilometers.

Asking the question, what are asteroids, a person involuntarily thinks about how the term appeared, what it means. It is translated as "star-like", and it was introduced in the XVIII century by an astronomer named William Herschel.

Comets and asteroids can be seen as point sources of a certain light, more or less bright. Although in the visible range, these celestial bodies do not radiate anything - only reflect the sunlight that falls on them. It should be noted that comets differ from asteroids. The first is their different appearance. The comet is easy to recognize by the brightly shining nucleus and the tail that comes from it.

Most of the asteroids that are known to astronomers today are moving between the orbits of Jupiter and Mars at a distance of about 2.2-3.2 a. Ie ( astronomical units) from the Sun. To date, scientists have discovered about 20 thousand asteroids. Of these, only fifty percent are registered. What are asteroids with registration? These are celestial bodies that have been assigned numbers, and sometimes even own names. Their orbits are calculated with very high accuracy. It should be noted that these celestial bodies are usually named after their discoverers. The names for asteroids, as a rule, are taken from ancient Greek mythology.

In general, from the above definition it becomes clear what asteroids are. However, what is still characteristic of them?

As a result of the observations made by these celestial bodies through the telescope, an interesting fact was discovered. The brightness of a large number of asteroids can change, and in a very short time - it takes several days, or even several hours. Scientists have long suggested that these changes in the brilliance of asteroids are associated with their rotation. It should be noted that they are conditioned, in the first place, by their irregular forms. And the first photographs, on which these heavenly bodies were imprinted (images taken with the help of spacecraft), confirmed this theory, and also showed the following: the surfaces of asteroids are completely dug by deep craters and funnels of various sizes.

The largest asteroid found in our solar system was previously considered the heavenly body of Ceres, whose dimensions were about 975 x 909 kilometers. But since 2006, she received a different status. And began to be called a dwarf planet. And the other two large asteroid (under the names Pallas and Vesta) have a diameter of 500 kilometers! Another interesting fact should also be noted. The fact is that Vesta is the only asteroid that can really be observed with the naked eye.