Do meteors heat up due to friction in the atmosphere, are they still hot when they reach the ground and why are most meteors weak
The article first appeared on January 15, 2005 as the 13th episode of the Mysteries of Space series
Do the meteors heat up because of the friction in the atmosphere?
It sounds logical, but still, it's not true.
Meteorites are tiny pieces of dust, ice rock, or metal that unfortunately fell into Earth's orbit. When these particles cross our atmosphere the particles heat up so much that they glow (at which point they are called meteors) and are visible for hundreds of kilometers.
However, it is not the friction that warms them. You can think of it this way: the space shuttle tiles are delicate and crumble easily by hand. If they were heated by friction as the shuttle reenters the atmosphere at Mach 25, they would disintegrate. It's not exactly good planning. Actually the air pressure is what heats the meteorites. When the gas is compressed it heats up, just what a bicycle pump does to inflate the tire. A meteorite traveling at 15 kilometers per second or more compresses the air in front of it violently. The air itself heats up and this causes meteoric warming. That's the fact, not the friction.
Are meteorites still hot when they hit the ground?
Something that has gotten so hot that it glows can be expected to still be hot two minutes later. Actually the situation is a bit more complicated. The very hot air in front of the meteor did not come into contact with the bone at all. (A particle can be called a meteorite when it crosses the atmosphere and lands on the ground, while a meteor describes the entire luminous process).
The rapid movement of the meteorite creates a shock wave in the air, like from a supersonic jet. The compressed air is in front of the meteorite, at a distance of a few centimeters (depending on the size of the meteorite) in a kind of tie - when the distance does not change. Between the shock wave and the surface of the meteorite there is an air pocket whose particles move relatively slowly.
The surface of the meteorite is melted by the heat of the compressed gas in front of it, and the air flow blows away the melted part in an evaporation process (ablation). The great speed of the meteorite provides the energy for all the heat and light that consumes the speed. When the shock wave slows down to below the speed of sound, it disappears, the heating and vaporization stops and the meteorite falls relatively slowly, perhaps at a speed of several hundreds of kilometers per hour. It is still high in the atmosphere at this point, and it takes several minutes for it to fall to the ground. Remember, a small piece of rock has spent a long time in space, and its core is quite cold, the parts that were heated anyway have already vaporized and disappeared. Moreover, the air above is cold, which in itself cools the rock.
All these processes together mean that the rock will not be hot when it hits the ground, in fact it can be very cold. Some meteorites have even been found surrounded by ice.
Why does a meteor shower look more like a trickle?
When a meteor shower is announced in the media, it seems to many that the sky will be full of meteors crossing the sky from their point of origin. Unfortunately, in almost most cases, the average meteor shower is far from that.
Typically, if the night is clear and you are out of town you can see 3-6 meteors in an hour's viewing. On some nights the rate may pick up a bit, and then the astronomers will say it's a meteor shower.
In mid-August and mid-December for example, you can notice that the meteors are especially numerous, sometimes they arrive at a rate of one per minute. In fact, these are the periods of the two biggest meteor showers of the year, although you don't always notice a real shower like rain. On rare occasions, when Earth crosses a compact trail of dust scattered by a recently passing comet, the meteors will appear to fall from the sky like rain. Unfortunately, such opportunities are rare. In recent years, the Leonid meteor shower in mid-November has provided some impressive meters. Although not like snowflakes. The rate of meteors reached thousands per hour in 1999 and again in 2001.
Meteors in Astropedia
