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Atmospheric absorption

The atmosphere of the earth protects us from many harmful types of radiation but it is also most important that it is transparent to ranges of wavelengths which are in use by astronomers to study the Universe. Two such regions are the visible region of the spectrum and the radio or microwave area.
The optical window extends from around 3x10-6 m to about 10-7 m while the radio window is transparent to radiation with wavelengths between 1 cm and 10 m.

The fact that the atmosphere is only transparent to relatively small bands of wavelength limits the study of the Universe. Since all wavelengths below the visible are effectively blocked X ray and gamma ray astronomy have only been possible in the last forty years. The study of astronomical X ray sources is done from detectors placed in satellites in orbit around the Earth.

(The diagram above has been simplified).

© Keith Gibbs 2010