Kellermann, Kenneth National Radio Astronomy Observatory, Charlottesville, Virginia.
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- Historical background
- Solar system radio astronomy
- Radio emission from the Milky Way
- Atomic and molecular gas
- Fast radio bursts
- Galaxies, quasars, and active galactic nuclei (AGN)
- Cosmic microwave background radiation
- Epoch of reionization
- Links to Primary Literature
- Additional Readings
The study of celestial bodies by examination of the energy they emit at radio frequencies. Radio astronomy observations cover the entire radio spectrum from less than 1 mm, where the cosmic signals become heavily attenuated by the atmosphere, to wavelengths of tens of meters, beyond which the incoming signals are attenuated by the ionosphere. However, radio waves between about 1 cm and 1 m in wavelength not only get through the Earth's atmosphere and ionosphere with little distortion, they also penetrate much of the gas and dust in space as well as the clouds of planetary atmospheres. Radio astronomy can therefore sometimes give a much clearer picture of stars and galaxies than is possible by means of conventional observation using visible light. Sophisticated antennas equipped with very sensitive radio receivers that are used to detect cosmic radio emission are referred to as radio telescopes (Fig. 1). See also: Atmosphere; Earth; Galaxy; Ionosphere; Radio telescope; Star; Wavelength
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