An Eye-Opener: Technology Meets the Telescope : The Silicon Chip Is Revolutionizing View of the Universe

The need to explain how we fit into the universe is no different now than it was 20,000 years ago. What’s different is the stories we tell.

--Ed Krupp, director,

Griffith Observatory.

A quiet revolution is under way in what may be the oldest of scientific endeavors.

It began when the first human gazed at the heavens and wondered what it all meant.

It reached its adolescence toward the end of the last century with the creation of large telescopes in the possibly arrogant assumption that scientists could answer that profound question.

And it is reaching its maturity today in what many regard as the golden age of astronomy. The marriage of electronics with optics, the birth of the Space Age and the construction of powerful new instruments have so widened the window on the universe that nearly every day brings new discoveries that would have confounded scientists just a decade ago.

The result so far has been an astounding metamorphosis of mankind’s understanding of a vast universe of which planet Earth is such a tiny part. And new technologies on the immediate horizon promise results that will eclipse what has been learned since the revolution began just a few years ago.

Recent discoveries have “completely transformed our ideas of what the universe is all about,” said John T. Jefferies, director of the National Optical Astronomy Observatories.

When astronomers look at the sky, they no longer see a “benign universe,” Jefferies said in an interview in Tucson, where he directs a wide range of U.S. observatories on two continents.

The old perception of a quiet universe has given way to “a picture of violently active galactic processes,” he said.

“It’s not at all a peaceful and calm place,” he added.

Dynamic Environment

Astronomers now know that the universe is a dynamic environment populated by trillions of galaxies, each comprised of trillions of stars, some traveling at near the speed of light. It is a universe of life and death, in which stars are born and die violently with the release of enormous amounts of energy. It is a universe so vast that distant stars are seen in modern telescopes as they were billions and billions of years ago, because it has taken that long for light--traveling 186,000 miles per second--to reach Earth.

The modern age of astronomy owes as much to electronics as it does to optics. Computers have removed astronomers from the cages alongside giant telescopes, where scientists had to brave the cold night air to run their machines, and placed them in warm rooms behind consoles that guide their scopes, collect their data and refine their discoveries.

Electronics has even replaced the camera, substituting a silicon chip for film.

By using silicon integrated circuits, called “charged coupled devices,” astronomers now literally count the number of light particles received from celestial objects.

Bruce Atwood, a physicist at the Cerro Tololo Inter-American Observatory in Chile, said the use of silicon chips in telescopes has been the most important development in astronomy in decades.

“It has led to a revolution in astronomy,” Atwood said during a recent interview at the U.S.-owned observatory in the Chilean Andes.

Good Light Detector

The chips were initially designed for computers, not telescopes, but “we found that silicon is a good detector of light,” Atwood said.

That discovery allowed astronomers to move from “low-sensitive photographic plates” to electronic detectors that capture nearly all of the light that the telescope receives from the target, Atwood said.

“That gives us the highest sensitivity that physics allows us to have,” he added.

Light travels in tiny particles, called photons. When photons hit the light-sensitive chemicals on a photographic negative, the negative records the intensity of the light at different points, thus producing an image. But most of the light is lost due to the low sensitivity of the film.

When light hits one of thousands of tiny detectors on a silicon chip, it produces electrons in quantities dependent upon the intensity of the light at that point. Those electrons represent nearly the entire amount of light striking that area.

“You take that packet of electrons and make an electronic image of far greater sensitivity than would be possible with photographic plates,” Atwood said.

The current generation of silicon chips are tiny, about half the size of a 35mm negative, but each chip has about 160,000 detectors, Atwood said. The next generation of chips will have more than 2 million detectors.

The new technology has made old telescopes far more powerful than when they were new, opening up “a whole new range of science,” said Jefferies, the director of the national observatories.

On Fringe of the Universe

When a silicon light detector is added to an old 36-inch telescope, the instrument is instantly transformed to the “equal of about a five-meter telescope,” the size of the largest telescope in the United States, Jefferies said.

And chips have made the larger scopes even more powerful, allowing astronomers to examine objects on the fringes of the universe.

Yet optical telescopes are useful only in the narrow band of the electromagnetic spectrum that we know as visible light, and in recent years astronomers have moved into areas that cannot be seen by the human eye. Using radio telescopes, for example, they “see” a universe as it would be seen if the human eye responded to long radio waves rather than the shorter waves of visible light.

That has made it possible for them to peer through the clouds of galactic dust that block visible light, thus permitting them to study such things as the murky center of the Earth’s Milky Way galaxy. Radio telescopes have sprung up around the world during the past few years, and the largest one of all, a system of 27 antennas spread across a New Mexico plain, is being expanded into a global network. When completed in a few years, the antennas will work together, in effect turning the Earth into a huge radio telescope.

The dreamers in the world of astronomy would like to take that a step further and put two antennas in widely separated orbits around the Earth, thus creating a network of enormous sensitivity. The visionaries among them think one of those antennas should be launched into space by the United States, the other by the Soviet Union.

Fittingly, the birth of the space age has opened new vistas to astronomy by allowing scientists to put some of their instruments in space where they are above the Earth’s atmosphere. It also made it possible for humans to walk on the moon, and robots to visit distant planets.

‘Amazing Period to Be Alive’

“This is an amazing period to be alive,” said Griffith’s Krupp, who specializes in historical astronomy. “A couple of decades ago, these were only dreams.”

Although the planetary probes rank among the most glamorous triumphs in the history of astronomical research, other space projects have yielded significant scientific results by simply allowing astronomers to put their instruments where the action is.

The Earth’s atmosphere prevents wide areas of the electromagnetic spectrum from reaching the ground, including infrared light, X-rays and gamma rays. Yet some of the more exotic objects in the universe reveal many of their secrets only in those ranges. The Space Age made it possible to put telescopes in orbit, and that led ultimately to the decision to build a large space telescope that could study the universe in all wavelengths.

The Hubble Space Telescope, the $1.2-billion crown jewel of the U.S. astronomical program, was to have been launched this fall by the space shuttle. That has been delayed for at least two years by the grounding of the shuttle, but the telescope still has top priority within the National Aeronautics and Space Administration.

Although the telescope will be less than half the size of the nation’s largest observatory at Mt. Palomar in northern San Diego County, the space telescope is expected to give scientists their best view yet of the most distant objects in the universe.

“It will be like opening your eyes for the first time,” Griffith’s Krupp said.

Just a few years ago engineers believed they would never be able to build scopes as large as those planned today because of gravitational and thermal deformation of the giant mirror. But the new generation of big scopes will use many mirrors, not just one.

Keck Telescope in Hawaii will use 36 hexagonal mirrors, each computer driven so that they will operate as a single mirror.

The National New Technology Telescope planned by the National Science Foundation will actually consist of four 7.5-meter telescopes in a four-barrel configuration that will form one 15-meter scope. It will be built either in Hawaii or Arizona.

Project engineer Larry Barr said one major advantage of that design is that “we can instrument each of the four barrels differently.” That will permit astronomers to study their targets by simultaneously using up to four different techniques.

The giant scope could help answer one of the most intriguing questions in all of astronomy.

Jefferies, the director of the national observatories, said it may be possible to find other planets circling other stars, thus indicating whether planetary systems are common or rare. That, in turn, will help determine the odds of life existing elsewhere.

“We must learn whether we are alone in the universe,” Jefferies said. “The implications are profound.”