By Fritzy Lingnau
(Photo by Pierluigi D’Amelio on Pixabay)
In the early 1930s, young engineer Karl Jansky discovered radio astronomy in his efforts to find natural radio interference that might disrupt overseas telephone calls. The receiver he built spanned 100 feet and made a full rotation every 20 minutes, recording radio waves with a pen and chart. With this machine, he noticed not only radio interference from lightning storms but also what he called “star noise”, a faint but mysterious noise emanating from outer space. For the first time in astronomical history, there was something new to be explored, completely invisible to the eye.
For the first time in astronomical history, there was something new to be explored, completely invisible to the eye.
Though the discovery of cosmic radio waves was brand new, the astronomical community wasn’t entirely invested. However, 7 years later, radio engineer Grote Reber began to meticulously investigate these sources of noise (APS). Presenting his own findings more widely in astronomy journals, radio astronomy progressed into a respected field, with the National Radio Astronomy Observatory founded in 1956 (Scoles). Currently, many scientists are involved in radio astronomy, cataloging celestial objects and investigating their properties. Radio astronomy is responsible for numerous crucial discoveries: pulsars, quasars, exoplanets, and cosmic microwave background radiation, a remnant of the Big Bang.
Radio astronomy was discovered from the creation of man-made radio transmissions, which harness a specific type of electromagnetic wave. Radio waves are a part of the electromagnetic radiation spectrum, defined by their long wavelength size (the distance between two crests) and low energy. Greatest to least in wavelength size, radio waves are followed by microwave, infrared, visible light, ultraviolet, x-ray, and gamma rays. Sound communication utilizes radio waves because they are easy to make and travel well, interacting little with matter (Libretexts).
Many types of celestial objects emit electromagnetic radiation; however, they don’t all emit the same amount or wavelength(s). Identifying these waves helps astronomers understand the motion and composition of far-off cosmic objects with the use of receiver telescopes. Using radio waves, astronomers observe cold hydrogen gas, (the most widespread element in the universe) allowing them to understand the structure of the universe based on the distribution of hydrogen (Hubble). Cosmic radio wave readings are made more accurate by increasing the size of receivers, which involves expensive materials, or by using interferometry arrays of telescopes that function together as a single telescope, reducing cost.
Individual Discoveries
As radio astronomy has developed and become more advanced, many have taken on the challenge begun by Karl Jansky and Grote Reber in investigating cosmic radio waves. Several extraordinary discoveries have been made by radio astronomers' efforts to observe the universe. In 1962, the bright radio source, “Star 3C 273,” was observed by Australian astronomers Hazard, Mackey, and Shimmins. They discovered the source came from two, rather than one radio source, set extremely close together. Through later projects and collaboration, the celestial phenomenon of quasars, “quasi-stellar objects” was formalized. Supermassive black holes centering entire galaxies end up expelling excess gas and dust from two sides at extreme velocities, emitting all kinds of electromagnetic waves (Smith).
Another notable discovery of radio astronomy is cosmic microwave background radiation or CMB, the heat left over from the Big Bang. Noticed by Penzias and Wilson in 1965, CMB serves as evidence for the theory of the universe’s origin. CMB has been detected in all parts of the sky, at all times of the day. The constant signal of CMB signifies that the universe was originally very dense and very hot, later expanding and becoming cooler over time (ESA).
In 1967, Jocelyn Bell Burnell, a graduate student studying quasars, discovered a strange “pulsing” signal that she originally believed might have been a message from an alien civilization. However, pulsars were later realized to be an entirely new celestial object on their own. They were identified as post-supernova star cores, made of densely packed neutrons, rapidly spinning and emitting radio waves, appearing to “pulse” to a radio telescope. (NRAO).
In 1992, pulsars led to another important discovery. Exoplanets (planets outside our own solar system) were confirmed by two radio astronomers, Wolszczan and Frail. They observed a pulsar that emitted irregularly timed radiation. Upon further investigation, this was due to two planets orbiting it (Wenz). Many significant discoveries in the field of radio astronomy were purely accidental (pulsars, exoplanets, and even radio waves themselves), which gives some insight into just how mysterious the study of the universe is. To this day, we have yet to uncover all that exists behind the radio emissions currently received by telescopes.
Looking to the Future
At present, a few notable arrays include the Atacama Large Millimeter/submillimeter Array in Chile, one of the most powerful radio telescopes; the NRAO’s Karl G. Jansky Very Large Array in New Mexico; and China’s Five-hundred-meter Aperture Spherical Telescope, nicknamed the “Eye of Heaven”, the world’s largest single-dish radio telescope. Each of these telescopes supports a host of advanced projects and experiments on cosmic radio emissions (Bradaschia).
One important ongoing project is the Square Kilometer Array, expected to become the largest radio astronomy observatory in the world (spread out across Australia and Africa). The huge area covered by the array will gather extremely specific readings, which will provide us with much finer details of the universe (Wild). A challenge that comes with ambitious projects like these is the money and international cooperation needed to build these large-scale telescopes, which are necessary to provide us with high-resolution pictures.
Another major challenge to these projects is the increasing presence of satellite groups and other forms of manmade interference. The issue of Radio Frequency Interference, or RFI, is exemplified by increasing emissions from cell phones, aircraft, satellites, and other observatory equipment. RFI mitigation is being experimented with using AI deep learning methods which though not yet mainstream, show promising results in the detection of RFI (Tuccari).
Radio astronomy has strengthened many aspects of technology, computer science, and engineering, and uncovered a substantial amount of knowledge about how electromagnetism exists in the cosmos. Hopes for radio astronomy as a field mostly revolve around the improvement of receivers and RFI mitigation techniques to understand more distant and more specific celestial objects. Future observations of “star noise” may one day result in monumental changes to our civilization– the discovery of livable exoplanets, entirely new phenomena out there, or even alien life.
References
American Physical Society. “May 5, 1933: New York Times Covers Discovery of Cosmic Radio
Waves.” APS News, vol. 24, no. 5, May 2015,
Bradaschia, F. (2013, September 15). Largest radio telescopes in the world. Radio2Space.
Cosmic Microwave Background (CMB) radiation. (n.d.). The European Space Agency. Retrieved
October 17, 2023, from https://www.esa.int/Science_Exploration/Space_Science/Herschel/Cosmic_Microwave_Background_CMB_radiation#:~:text=The%20CMB%20radiation%20was%20discovered,or%20night%2C%20summer%20or%20winter
Libretexts. (2018, September 22). 23.2: Electromagnetic Waves and their Properties.
Scoles, S. (2018, August 22). The Rebirth of Radio Astronomy. WIRED.
Smith, D. (2013, March 15). Fifty Years of Quasars. California Institute of Technology.
The Electromagnetic Spectrum. (n.d.). Hubble. Retrieved October 17, 2023, from
The History of Radio Astronomy. (2016, March 24). National Radio Astronomy Observatory.
Tuccari, G., & Tuccari, G. G. (2022). Latvian Journal of Physics and Technical Sciences, 59(s3),
82–95. doi:10.2478/lpts-2022-0027
Wenz, J. (2019, October 8). How the first exoplanets were discovered. Astronomy Magazine.
What is Radio Astronomy? (n.d.). CSIRO Astronomy and Space Science. Retrieved November 4,
Wild, S. (2022, December 6). Construction of World’s Largest Radio Observatory Is Finally
Under Way. Scientific American. https://www.scientificamerican.com/article/construction-of-worlds-largest-radio-observatory-is-finally-under-way1/
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