Electromagnetic Radiation
- Generated by processes at the atomic level
- Changes in the way parts of an atom interact and move
- Forms of electromagnetic radiation are described by the electromagnetic spectrum
- Low energy --> low frequency
- High energy --> high frequency
- Particles are photons
- Types of radiation emitted by astronomical objects is determined by their temperature
| Type of Radiation | Wavelength Range (nm) | Radiated by Objects at This Temperature | Typical Sources |
|---|---|---|---|
| Gamma Rays | Less than 0.01 | More than $10^8$ K | Nuclear reactions |
| X-rays | 0.01-20 | $10^6-10^8$ K | Gas clusters in galaxies, supernova remnants, solar corona |
| Ultraviolet Rays | 20-400 | $10^4-10^6$ K | Supernova remnants, very hot stars |
| Visible light | 400-700 | $10^3-10^4$ K | Stars |
| Infrared | $10^3-10^6$ | $10-10^3$ K | Cool clouds of dust and gas, planets, moons |
| Microwaves | $10^6-10^9$ | Less than 10 K | Active galaxies, pulsars, cosmic background radiation |
| Radio Waves | More than $10^9$ | Less than 10 K | Supernova remnants, pulsars, cold gas |