small planets are about 400 thousand, and the projected and theoretical estimates of several billion.

Classification



Since all known minor planets differ in their characteristics, size, structure, location in the solar system and the shape of the orbit, they are divided into large classes in which they are arranged in order of distance from the sun.

closest to the Sun Belt is vulcanoid so called minor planets, which lie inside the orbit of Mercury.Computer calculations and theory show that lies between the Sun and Mercury, the region has a stable gravity and, therefore, more likely, small celestial bodies exist there.Finding them is difficult in practice the proximity of the sun, and no vulcanoid not yet been investigated and were found.

next group called Aton, these small planets the major axis of the orbit of less than astronomical uni
t.In most parts of the way so Aton closer to the Sun than the Earth, and many of them do not intersect the Earth's orbit altogether.

Trojans Mars are named so because of the fact that the libration points collected from Mars.Such planets are projected to not more than 10, and is known for about half of them.

Groups Cupid and Apollo make the asteroid belt between the orbits of Mars and Jupiter.Sometimes all small planets called asteroids, in which case the zone is called the "main asteroid belt."This designation was popular and was considered the only correct as long as there have not been discovered Kuiper Belt and Centaur.From a technical point of view, this designation is incorrect, as there are bodies in the Kuiper Belt, which in all respects superior to the largest asteroid, and the sheer number of its constituent objects exceeds the number of the main asteroid several orders of magnitude.

class of minor planets beyond the asteroid belt, called the Jupiter Trojans, or simply Trojans, they are grouped at the libration points of Jupiter.Between the orbits of Jupiter and Neptune is belt Centaurs.The first of the Centaur Chiron was discovered, but when approaching the sun, he showed cometary activity.Despite this, the list of Centaurs, was not deleted and is the Centaur and Comet at the same time.Next come the Neptune Trojans known them until 6 and beyond Neptune are located trans-Neptunian objects.Most of those who are already known to form the Kuiper Belt.Koyperoidy divided into classic, scattered and resonance.

There are trans-Neptunian objects, which, because of the peculiarities of movement can not be attributed to any of these three classes.A famous example of this - Sedna, a small planet's orbit that lies beyond the Kuiper Belt, and it is the only such body of the Solar System.

difficult to relate to other groups because of remoteness from the Sun Damokloidy whose orbits are very elongated.At aphelion they go beyond Uranus, and getting closer to perihelion of Jupiter and Mars.

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Mars Trojans are the most insignificant among the parameters of minor planets.Eureka, the largest of them, is 1.3 km in diameter.Following are the Aten with the largest body Kruitna, 5 km.The following Sisyphus of Apollo, having a size of 8.2 km, and Ganymede of Amur - 39 km.

Asteroids, Centaurs, and Trojans of Jupiter and Neptune have much larger sizes.More than a hundred of them exceed the size of 100 km.Even larger sizes from trans-Neptunian objects, for example, plutino Orcus of the Kuiper belt has a diameter of 1526 km.

structure of small planets is different.Aten, Apollo, Damokloidy, centaurs and cupids and all the asteroids have an irregular shape and have no internal structure.Their appearance and the inner part of very little is known of their great distance.