Radio Astronomy - Origins Of Radio Astronomy, Radio Vs. Optical Astronomy, Radio Telescopes, Increasing Resolution In A Radio Telescope
waves visible light frequencies
Radio astronomy is the field of science in which information about the solar system and outer space is collected by using radio waves rather than visible light waves. In their broadest principles, radio astronomy and traditional optical astronomy are quite similar. Both visible radiation and radio waves are forms of electro-magnetic radiation, the primary difference between them being the wavelength and frequency of the waves in each case. Visible light has wavelengths in the range between about 4,000 and 7,000 angstroms and frequencies in the range from about 1014 to 1015 cycles per second. (An angstrom is a unit of measurement equal to 10-8 centimeter.) In contrast, radio waves have wavelengths greater than 1 meter and frequencies of less than 109 cycles per second.
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The presence of radio sources in outer space was an important breakthrough for astronomers. Prior to the 1930s, astronomers had to rely almost entirely on visible light for the information they obtained about the solar system and outer space. Sometimes that light was collected directly by the human eye, and others time by means of telescopes. But in either case, astronomers had at their disposal o…
Radio telescopes and optical telescopes have some features in common. Both instruments, for example, are designed to collect, focus, and record the presence of a certain type of electromagnetic radiation—radio waves in one case and light waves in the other. However, the details of each kind of telescope are quite different from one other. One reason for these differences is that the human e…
A major drawback of the radio telescope is that it resolves images much less well than does an optical telescope. The resolving power of a telescope is its ability to separate two objects close to each other in the sky. The resolving power of early radio telescopes was often no better than about a degree of arc compared to a second of arc that is typical for optical telescopes. Since the resolving…
The availability of radio telescopes has made possible a number of exciting discoveries about our own solar system, about galaxies, about star-like objects, and about the interstellar medium. The solar system discoveries are based on the fact that the planets and their satellites do not emit visible light themselves (they only reflect visible light), although they do emit radio waves. Thus, astron…
Some of the earliest research in radio astronomy focused on the structure of our galaxy, the Milky Way Galaxy. Studying our own galaxy with light waves is extraordinarily difficult because our solar system is buried within the galaxy, and much of the light emitted by stars that make up the galaxy is blocked out by interstellar dust and gas. Radio astronomy is better able to solve this problem beca…
One of the earliest discoveries made in radio astronomy was the existence of unusual objects now known as radio galaxies. The first of these, a strong radio source named Cygnus A, was detected by Grote Reber in 1940 using a homemade antenna in his backyard. Cygnus A emits about a million times as much energy in the radio region of the electromagnetic spectrum as does our own galaxy in all regions …
Some of the most interesting objects in the sky have been discovered by using the techniques of radio astronomy. Included among these are the quasars and pulsars. When quasars were first discovered in 1960, they startled astronomers because they appeared to be stars that emitted both visible and radio radiation in very large amounts. Yet there was no way to explain how stars could produce radio wa…
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