Radio Astronomy on the Cheap

Mercury, May/June 2004 Table of Contents

Courtesy of NRAO/AUI/NSF

by James Brown

Most of us rely on visible electromagnetic radiation to tell us and our students something about the Cosmos, but sophisticated (and inexpensive) radio observations are now possible and offer us a new view of the heavens.

Radio astronomy had its birth in 1932 when Karl Guthe Jansky built an antenna for Bell Labs. The instrument was designed to receive radio waves at a frequency of 20.5 MHz and be part of an investigation into the potential use of "short waves" for transatlantic radiotelephone service.

Turning his antenna skyward, Jansky discovered a signal that repeated not every 24 hours, but every 23 hours and 56 minutes. This is characteristic of rotation of Earth relative to the stars and other objects far outside our solar system. He eventually figured out that the radiation was coming from the Milky Way and was strongest in the direction of the center of the Galaxy, toward the constellation Sagittarius.

Grote Reber learned about Jansky’s discovery and wanted to continue the work and learn more about "cosmic" radio waves. Yet Reber was unable to find employment with astronomical observatories to study the waves because none of the observatories were hiring in the middle of the Great Depression. He decided to study radio astronomy on his own, and in 1937 he built his own radio telescope in his backyard in Wheaton, Illinois.

Reber spent long hours every night scanning the skies with his telescope. He had to do the work at night because there was too much radio interference from the sparks in automobile engines during the daytime. From 1938 to 1943, Reber made the first surveys of radio waves from the sky and published his results both in engineering and astronomy journals. His work was so robust that his accomplishments insured that radio astronomy would become a major field of research following World War II. Research groups in many countries began building bigger and better antennas and receivers to follow up on Reber’s discoveries. And the rest, as they say, is astronomical history.

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