Mammoth Dishes Herald Cosmic Discovery ; A New Generation of Supersize Radio Telescopes Will Give Astronomers the Ability to Peer to the Edges of Space

Article excerpt

For nearly 70 years, astronomers have made some of their most significant discoveries by tuning in to the universe with telescopes that gather radio waves instead of light.

Through these sensitive receivers, scientists have detected the big bang's afterglow, improved their ability to measure the universe's expansion, and rigorously tested Albert Einstein's theory of general relativity. Three of the five Nobel Prizes given to astrophysicists have been awarded for cosmic discoveries made at radio frequencies.

Now, a new generation of radio telescopes is moving from design sketches to construction sites, with the first scheduled to be dedicated this month.

The devices are engineering marvels - some using thousands of tiny pistons to keep football-field-size dishes from warping in heat and wind, and others using complex computer programs to link hundreds of smaller dishes. And they are expected to open a fresh round of discoveries as scientists probe the farthest reaches of space and search for extraterrestrial life.

*In Green Bank, W.Va., the National Radio Astronomy Observatory (NRAO) is slated to dedicate a new, 100-yard-wide dish this month. It is the largest fully steerable radio telescope in the world, observatory officials say.

*High in Chile's Atacama Desert, the NRAO and the European Southern Observatory are building an array of as many as 64 dishes, each 12 yards wide. They can be spread over an area more than six miles across.

*In California, the University of California at Berkeley and the Search for Extraterrestrial Intelligence (SETI) Institute are building an array of 500 to 1,000 small radio telescopes, scheduled to begin operating in 2005. The primary goal is to search for signals from alien civilizations.

*Astronomers from five countries and a consortium of European nations last week signed a pact to begin planning the mother of all radio telescopes - a connected array of dishes that, taken together, would yield a combined area of 1 square kilometer.

"It's a new age for radio astronomy," says Alyssa Goodman, who studies the cosmos in radio wavelengths at the Harvard- Smithsonian Center For Astrophysics in Cambridge, Mass.

Much of the groundwork for these new instruments has been laid during the past two decades. During that time, astronomers have solved a number of technical puzzles that prevented them from observing the full spectrum of electromagnetic waves that penetrate Earth's atmosphere.

"Now what we're doing is building the facilities that allow us to go beyond the preliminary observations we've been able to make," says Lincoln Greenhill of the Center for Astrophysics.

Frontiers of exploration

Those preliminary observations have given astronomers much to explore.

For example, astronomers had once thought that molecules couldn't exist in interstellar space, because the radiation from stars would break them apart. …