When meteors enter the atmosphere at high speeds, their surfaces heat up to thousands of degrees, although for large enough bodies, their interiors may remain very cold. Only the surface few inches or so is usually involved in the few seconds that the body streaks through the atmosphere. A tremendous amount of energy is dumped into the local atmosphere, usually causing flash ionization of the oxygen and nitrogen atoms there. This volume of space, even for a dust grain-sized meteor, can subtend many tens of meters in diameter. That's why you can see them so dramatically from the ground 70 kilometers away or more.
Copyright 1997 Dr. Sten Odenwald
Return to Ask the Astronomer.