Solar Radio Astronomy’ 
By ALAN MAXWELL 
Radio Astronomy Station of Harvard College Observatory 
Fort Davis, Tex. 
[With 2 plates] 
THE BEGINNINGS of radio astronomy are to be found in the work of 
James Clerk Maxwell, Faraday, and Hertz. A few years after 
Hertz’s pioneer work on radio waves, astronomers were speculating 
whether the solar corona could be the source of electromagnetic dis- 
turbances and emit radio waves. About 1900 Sir Oliver Lodge at- 
tempted to observe such waves, but this attempt was doomed to failure 
by the inadequacy of the available radio techniques. Subsequently, 
the idea of searching for extraterrestrial radio emissions was aban- 
doned, and for many years astronomers showed no further interest 
in the matter. 
In 1932, Jansky, investigating atmospherics at a wavelength of 15 
meters, found that the noise which his antenna system picked up 
showed a variation whose periodicity was not exactly 24 hours, but 
was 23 hours 56 minutes, corresponding to the period of the earth’s 
rotation relative to the stars. Jansky concluded that this radio noise 
came from the Milky Way, and suggested that the radio waves were 
being generated either in the stars or in interstellar space. This work 
should have been of peculiar interest to astronomers, but it received 
little attention. It was followed up by one or two people, notably 
by Reber, but it was not until the years immediately following the 
Second World War that the tremendous astronomical significance of 
this early discovery was realized. 
In 1948, Bolton and Stanley, in Australia, announced that they had 
discovered an intense source of radio emission whose angular diameter 
in the sky was less than 8 minutes of arc, and whose position lay in 
the constellation of Cygnus. Shortly afterward, Ryle and Smith at 
Cambridge, England, discovered a second, even more intense, radio 
1The 26th annual James Arthur lecture on the sun, given under the auspices of the 
Smithsonian Institution on Oct. 15, 1959. 
299 
