Almost all observations are really observations of light, so we need to understand light to understand astronomy. A.1 Light is a wave. At low freqencies, no electrons are emitted. Higher frequency light has photons with higher energy. To make a wave, disturb the medium.
Light is caused by accelerating electrically charged particles.
Matter is made up mostly of charged particles which vibrate, rotate, and move. We feel this motion as temperature. The rate and freqency of light emitted depends only on the temperature of the blackbody. The hotter something is, the more light it emits. The frequency range emitted also depends on the temperature.