What Is a Meteor?

A meteor is the streak of bright light that can be seen from Earth when an object enters the atmosphere. The actual object entering the atmosphere is called a meteoroid , and it is usually a piece of an asteroid. The term meteor refers only to the image created by this entry – a bright light cascading from the sky – often referred to as a falling star.

The bright light of a meteor is a result of heat produced by the meteoroid entering the atmosphere. Rather than friction, this heat is produced by ram pressure: the pressure exerted on a body moving through a fluid medium. This pressure heats the meteoroid and the air around it to such a degree that the image of the meteor can be seen from earth.

Although meteoroids are often referred to as meteors or meteor rocks, this usage is not technically correct. While most meteoroid s come from asteroids, it has been speculated that some may come from comets, and others likely come from the Moon or Mars. When a meteoroid survives its fall to the earth, it is called a meteorite. The meteorites discovered on Earth are often categorized as either a fall or a find. A fall is a meteorite discovered after somebody witnesses its fall to the ground, while a find is a meteorite that is not witnessed.

On any given night, it is possible to see as many as one meteoroid per hour, and during a meteor shower, this rate can increase to as many as a hundred per hour. Although many meteoroids enter the earth’s atmosphere each day, most are too small to cause a visible image or to reach the earth's surface. Although meteoroid s enter the atmosphere at incredibly high speeds, topping 40 miles (70 km) per second, they usually slow to only a couple hundred miles per hour and reach the earth's surface with little impact. Extremely bright meteors can be called fireballs or bolides. While there are differing regulations as to what degree of brightness constitutes a fireball, it is clear that they are an impressive sight, but rare to behold.