"Falling stars" - such a poetic name was invented by people for meteoric bodies captured by the gravity of the Earth and falling into its atmosphere. The further fate of meteoric bodies is determined by their size: the smallest ones burn up in the atmosphere, the larger ones reach the earth's surface.
Any celestial body larger than cosmic dust, but inferior to an asteroid, is called a meteoroid. A meteoroid that falls into the earth's atmosphere is called a meteor, and a meteorite that falls on the earth's surface.
Travel speed in space
The speed of meteoroid bodies moving in outer space can be different, but in any case it exceeds the second cosmic speed, equal to 11.2 km / s. This speed allows the body to overcome the gravitational attraction of the planet, but it is inherent only in those meteoric bodies that were born in the solar system. For meteoroids that come from outside, higher speeds are also characteristic.
The minimum speed of a meteoric body when it meets the planet Earth is determined by how the directions of motion of both bodies are related. The minimum is comparable to the speed of the Earth's orbital motion - about 30 km / s. This applies to those meteoroids that move in the same direction as the Earth, as if catching up with it. There are most of such meteoric bodies, because meteoroids arose from the same rotating protoplanetary cloud as the Earth, therefore, must move in the same direction.
If the meteoroid moves towards the Earth, then its speed is added to the orbital one and therefore turns out to be higher. The velocity of bodies from the Perseid meteor shower, through which the Earth passes every year in August, is 61 km / s, and the meteoroids from the Leonid stream, which the planet meets between November 14 and 21, has a speed of 71 km / s.
The highest speed is typical for comet fragments, it exceeds the third cosmic speed - such that allows the body to leave the solar system - 16, 5 km / s, to which the orbital speed must be added and corrections for the direction of motion relative to the Earth.
Meteoroid in the earth's atmosphere
In the upper layers of the atmosphere, the air almost does not interfere with the movement of the meteor - it is too rarefied here, the distance between gas molecules can exceed the size of an average meteoroid. But in denser layers of the atmosphere, the friction force begins to affect the meteor, and its movement slows down. At an altitude of 10-20 km from the earth's surface, the body falls into the delay region, losing its cosmic speed and, as it were, hovering in the air.
Subsequently, the resistance of the atmospheric air is balanced by the earth's gravity, and the meteor falls on the surface of the Earth like any other body. At the same time, its speed reaches 50-150 km / s, depending on the mass.
Not every meteor reaches the earth's surface, becoming a meteorite; many burn up in the atmosphere. You can distinguish a meteorite from an ordinary stone by the melted surface.