Lessons Overview : Types of RadiationAlthough electromagnetic radiation is most often classified by its wavelength, it can also be classified based on how it is emitted. There are several processes that can cause objects to emit electromagnetic radiation.
Thermal radiation is produced by every object in the universe. The amount of thermal radiation emitted by an object depends on its temperature. Objects that are hotter in temperature emit more energetic (shorter wavelength, higher frequency) radiation than objects that are cooler. Astronomers often use thermal radiation to study objects like planets, which generally do not emit any other forms of radiation.
Synchrotron radiation is produced when charged particles accelerate around a very strong magnetic field. These particles are traveling at velocities approaching the speed of light. The amount of energy that a particle emits depends on the radius of its circular path through the magnetic field. If that radius is small, the particle can radiate a tremendous amount of energy. The most widespread source of radio waves in our galaxy is synchrotron radiation. All of the types of sources we will discuss in detail emit synchrotron radiation, which allows astronomers to learn a great deal about the objects that emit the radiation.
An electron, moving at relativistic speeds (near the speed of light) begins to spiral in the presence of a magnetic field (represented in this diagram by a series of field lines). As it spirals, the electron emits cones of synchrotron radiation.