As the fragment falls through the atmosphere it is heated and some of the material is vaporized. Explain how you could determine the composition of this hot vaporized material from the light it emits.

by determining the wavelength of the light emitted

Explanation:

The composition of the hot vaporized materials of an asteroid can be find out by the wavelength of the light emitted when the fragment material is burnt out.

Some of the asteroids that are very large do not burn completely in the atmosphere and they fall on the surface of the earth. Thus there is a possibility of radioactivity. An atom is radioactive or unstable when the forces that constitutes the nucleus are not balanced and then the nucleus have excess of energy. Thus these unstable and highly energetic nucleus will try to attain stability by ejecting protons and neutrons, or by releasing gamma rays, beta particles or positrons, etc. Thus they will radiate energy and will cause radioactivity.

your answer would be fusion