The Mechanisms of Electromagnetic Emissions

If the material in this chapter is unfamiliar to you, do not be discouraged if you don’t understand everything the first time through. Some of these concepts are a little complicated and few nonscientists have much awareness of them. However, having some familiarity with them will make your radio astronomy activities much more interesting and meaningful.

What causes electromagnetic radiation to be emitted at different frequencies? Fortunately for us, these frequency differences, along with a few other properties we can observe, give us a lot of information about the source of the radiation, as well as the media through which it has traveled.

Electromagnetic radiation is produced by either thermal mechanisms or non-thermal mechanisms.

Examples of thermal radiation include

• Continuous spectrum emissions related to the temperature of the object or material.

• Specific frequency emissions from neutral hydrogen and other atoms and molecules.

Examples of non-thermal mechanisms include

• Emissions due to synchrotron radiation.

• Amplified emissions due to astrophysical masers.