Glossary term: Radio Astronomy

Description: Radio astronomy is the branch of astronomy concerned with observations of radio waves, a special region in the electromagnetic spectrum. Earth's atmosphere has "radio windows": It allows radio waves in certain frequency (or wavelength) ranges to pass nearly unhindered. That fact allows for observations of such radio waves from astronomical objects with ground-based radio telescopes. Typical observing frequencies range from an upper limit of about 300 gigahertz (GHz) down to tens of megahertz (MHz). This corresponds to wavelengths of 1 millimeter (mm) to tens of meters, respectively. By going to particularly suitable dry, high-altitude locations, astronomers can even perform submillimeter observations, down to wavelengths of about 0.3 mm, corresponding to frequencies of up to 1 terahertz (THz). The lower frequency limit at about 10 MHz is due to Earth's so-called ionosphere. That high-altitude region within our atmosphere contains numerous charged particles, which reflect ultra-long radio waves right back into space. Radio astronomy enables us to observe the emission from cold gas in galaxies and the Milky Way, such as atomic hydrogen and molecular gas. In this way, astronomers can study the diffuse interstellar medium, as well as the regions and processes in which stars and planets are born. Radio astronomy also allows for the study of highly energetic objects such as pulsars and active galactic nuclei: In or around objects like those, electrons are accelerated in a strong magnetic field, leading to the emission of radio waves known as synchrotron radiation. Pulsars and the very bright active galactic nuclei known as quasars were discovered using radio astronomy, as was the remnant of our Universe's hot Big Bang phase, the cosmic microwave background (CMB). Although radio waves from space were first detected in the 1930s, radio astronomy only became a major branch of observational astronomy after 1950.

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Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".

Related Media

Panorama of the Parks Radio Telescope with blue sky and few thin clouds. The telescope looks like a giant satellite dish.

Parkes Radio Telescope

Caption: The 64m Radio Telescope at Parkes Observatory (New South Wales, Australia) is fully operantional since 1963 and continuously upgraded since. Also called "The Dish", it is run by the Commonwealth Scientific and Industrial Research Organisation (CSIRO). The telescope can be pointed at a part of the sky. The radio waves from this part of the sky are then reflected and focussed by the giant dish to a receiver at the focal point. The data from this receiver can then be analysed by astronomers.
Credit: David McClenaghan/CSIRO credit link

License: CC-BY-3.0 Creative Commons Attribution 3.0 Unported icons

Related Activities

SKAO and the mysteries of invisible light

SKAO and the mysteries of invisible light

astroEDU educational activity (links to astroEDU website)
Description: Discover the invisible light with SKAO, the largest radio telescope in the world!

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons

Age Ranges: 12-14 , 14-16
Education Level: Informal , Middle School , Secondary
Areas of Learning: Guided-discovery learning , Observation based , Technology-based
Costs: High Cost
Duration: several days
Group Size: Group
Skills: Asking questions , Constructing explanations