New Ear to the Heavens

In astronomy these days, the best results are often achieved by those who listen rather than look. The listeners are radio astronomers, whose vast antennas scan the skies for squawks, beeps and hums that tell them more about the universe than the eye can see. In the past decade, radio astronomers have made a host of discoveries: quasars, pulsars, free-floating molecules in the lonely reaches between the stars. They have even detected what may be a faint echo of the original Big Bang, the great explosion that some scientists think marked the creation of the stars and galaxies.

Now radio astronomers are getting a movable telescope that is bigger and more precise than any they have ever had before. It is a huge, 328-ft. paraboloid nestled in West Germany's Eifel hills at Effelsberg, about 25 miles southwest of Bonn. More than 75 feet larger than the existing record holder, Britain's big Jodrell Bank radio antenna, the steel-and-aluminum instrument is now undergoing its final checkouts before it begins scanning the heavens in earnest this fall.

Crude Beginnings. In spite of the physical differences, such sensitive radio telescopes operate much like their optical cousins. Instead of gathering ordinary light, they use their big reflectors to capture the radio energy from the invisible part of the electromagnetic spectrum. The curved surface of the antenna acts just like a lens, bringing the radio waves to sharp focus at a point in front of the dish. There they are picked up by a smaller antenna and piped into the telescope's electronic amplifier. The signals may be translated into audible sounds, traced out by pen-and-ink graph plotters and analyzed in detail by computers.

Meticulous Design. The first radio telescope, a crude antenna that turned on wheels cannibalized from a Model T Ford, was made 40 years ago by a Bell Labs scientist named Karl Jansky. In contrast, the new German instrument is a model of engineering sophistication. The entire telescope can be rotated a full 360DEG on a circular railroad-type track in only nine minutes. Its plate-and-mesh reflector can be tilted 90DEG from a point directly overhead to the horizon in only half that time. Furthermore, the telescope has been so meticulously designed that the stresses caused by such movements deform its reflector by no more than about four-hundredths of an inch, an important factor in maintaining a sharp "image." Not the least of the antenna's advantages is its site: located at the bottom of a tree-lined valley, it should be well shielded by the surrounding hills from commercial microwaves and other electronic pollution.

The remarkable new instrument is the result of an almost singlehanded campaign by the 60-year-old head of Bonn University's Institute of Radio Astronomy. Trying to restore some of Germany's prewar scientific luster, Professor Otto Hachenberg personally supervised the design, persuaded the Volkswagen foundation to pay most of the cost ($9 million), and nagged the builders to complete the complicated job from blueprints to operation in a short 3 1/2 years.

Radio astronomers expect great things of their newest tool. Present telescopes have detected 20,000 sources of radio emissions in the sky. Effelsberg should increase that number considerably.

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