In space there is a large number of asteroids and comets, but many of them rotate on certain orbits. From time to time some of them come into the view of astronomers as go towards Earth.
Asteroids leave habitual orbits, as a rule, having faced with each other, or under the influence of gravitation of large objects. Too small asteroids, with a diameter less than 150 meters, do not cause concerns as at hit in the atmosphere of Earth completely burn down, without reaching a surface. Larger asteroids constitute danger to Earth, its degree depends on the sizes of an object and distance on which it can come nearer. Asteroids of the average size can cause the effect similar to explosion of an atomic bomb. Large space objects, more than a kilometer in size, are capable to create global disaster: many animal species will die out, also industrial facilities will be erased from a face of the City land. The asteroids which are flying by from Earth at distance it is less than 0.05 astronomical units, are considered as potentially dangerous. Considering that one astronomical unit is equal to about 149.6 million km, critical distance to a dangerous object – 7.5 million km. For comparison, it is nearly 20 times farther than the Moon (distance to the Moon only 0.0026 and. e, or 384.47 thousand km). If the asteroid approaches Earth on perihelion distance, smaller or equal 1.3 astronomical units, it is considered the object approaching Earth. Theoretical such objects can face the planet, but practically they very seldom "reach" our planet. Now scientists study a possibility of their "capture", that is a conclusion to Earth orbit. If the asteroid which arrived from far space constantly is in an orbit, in parallel with the Moon, there will be a wonderful opportunity to investigate it, to extract minerals, etc. So far it is about "capture" of a small, 10th meter asteroid which in 2049 will approach Earth approximately on one million kilometers.