COSMIC CLOSE-UPS

By MICHAEL D. LEMONICK

THEY LOOK REMARKABLY LIKE GREAT TOWERING thunderheads, billowing high into the evening sky as they catch the last rays of the setting sun. They are so sharp, so startlingly three dimensional, that the mind wants to domesticate them, to bring them down to earth, to imagine them rising on the horizon or just beyond the wings of an airliner. These are no ordinary clouds, however. They stand not 30,000 ft. but almost 6 trillion miles high. They are illuminated not with ordinary earthly light but with searing ultraviolet radiation spewing from nuclear fires at the center of a handful of newly formed stars. And they're 7,000 light-years from Earth--more than 400 million times as far away as the sun.

This cosmic vista, seen in a photo released by NASA two weeks ago, is the latest in a series of stunning images captured from the ends of the universe by the Hubble Space Telescope. Once written off as a near total loss because of an inaccurately ground mirror, the Hubble has in the past two years redeemed itself spectacularly. It has offered close-up pictures of distant galaxies that are 10 times as sharp as those produced by earthbound telescopes--pictures that are not just scientifically significant but breathtakingly beautiful as well. In fact, the orbiting observatory has extended our view of the cosmos more dramatically than any single instrument since Galileo first pointed his crude, low-power telescope at the heavens.

The momentous sights revealed by the Hubble can stir anybody's imagination. These are rare glimpses of the outer boundaries of physical reality, and of the fiery cataclysms in which nature perpetually regenerates itself. Even astronomers have trouble keeping their professional cool when pictures like the new one--showing a section of the Eagle Nebula, a knot of interstellar gas and dust in the constellation Serpens--come beaming in from space. "When I saw it, I was just blown away," says NASA's Ed Weiler, the Hubble's chief scientist. The image has such visual impact, in fact, that some researchers tend to overlook its scientific importance.

THAT IMPORTANCE IS IMMENSE, however. Some of the smallest features visible in the photo--delicate, stalklike projections reaching out from the clouds--are actually infant star systems the size of our solar system, just now emerging from the gas and dust that shrouded their birth. The ability to see them in such unprecedented detail has told astronomers an enormous amount about how stars are born and why some are circled by planets and others are not. "People had come up with plausible theories about star birth," says Arizona State University astronomer Jeff Hester, leader of the team that took the picture. "Then we got this image--totally out of left field, totally unexpected. And suddenly you could see clearly what's actually happening."

If anyone still harbored lingering doubts about the Hubble's power to do groundbreaking science, the new photograph should put those doubts to rest. Without the Hubble this discovery would not have been possible--and neither would a score of others spanning virtually every branch of astronomy. The telescope has already thrown Big Bang theorists a curve by suggesting that some stars in the universe are older than the universe itself. At the core of one galaxy it has found a black hole as massive as 3 billion suns. It has made scientists front-row spectators at the collision of comet Shoemaker-Levy 9 and the planet Jupiter. And it has begun to unravel the riddle of the brilliant beacons of cosmic light known as quasars. Go to any astronomy conference these days, and you'll find half the scientific papers are based on space-telescope observations. "The Hubble," declares University of Arizona astronomer Rodger Thompson, "is fundamentally altering our view of the universe."

The Hubble still has at least a decade of useful life, and astronomers are convinced that before it's mothballed the telescope will answer many of the most profound mysteries of the cosmos: How big and how old is the universe? What is it made of? How did the galaxies come to exist? Do other Earth-like planets orbit other sunlike stars? "We made Congress a lot of bold promises about how much we'd learn from the Hubble," says John Bahcall, an astrophysicist at the Institute for Advanced Study in Princeton, New Jersey, and an early champion of the idea of a space telescope. "I'm quite relieved to be able to say we were right."

A little more than five years ago, Bahcall was singing a much more melancholy tune. In May 1990, shortly after the Hubble went into orbit, engineers and scientists realized that something was horribly wrong. The telescope simply wouldn't focus properly--the result, it turned out, of a light-gathering mirror that had been ground with exquisite precision, but in the wrong shape. After a lengthy investigation, the disaster was laid to a simple, dumb mistake: a technician had assembled a device that guided the mirror-grinding process with one bolt put on backward. The hobbled Hubble could still do some important science, but much of its research program appeared headed out the window. "I'd been working on this for almost two decades," says Bahcall. "I was devastated."

Others had even more at stake. Bahcall's friend and colleague Lyman Spitzer, an astrophysicist at nearby Princeton University, first began thinking about space telescopes nearly half a century ago. In 1945, just after World War II, a friend approached the young Spitzer asking for help. The Air Force had commissioned a study to look into how Earth-orbiting satellites--still a purely theoretical concept at that point--might be scientifically useful. Would Spitzer be interested in giving an astronomer's perspective? He instantly saw the potential of turning the satellites' gaze away from Earth toward deep space. "I wrote an appendix to the report," he recalls. It was titled "Astronomical Advantages of an Extra-Terrestrial Observatory."

There were, as he reported, two chief advantages. First, the earth's atmosphere is virtually opaque to much of the infrared and ultraviolet radiation that is an important part of the energy output of stars and gas clouds; a telescope orbiting above the atmosphere would be able to see the cosmos in all its colors--not just the ones visible to the human eye. Second, and more important, the atmosphere is like a thick blanket of gas, constantly swirling and churning. That's what makes the stars twinkle. But it also drives astronomers to distraction by blurring the images in their telescopes. A telescope soaring above this roiling sea of air could take crystal-clear pictures and, presumably, lift the veil on some of the universe's deepest secrets.

"I certainly convinced myself that a space telescope would be an important research tool," says Spitzer, still active in astrophysics at 82, "though I don't recall that the report had much impact at the time." All that changed when the Soviets launched Sputnik in 1957; suddenly just about anything involving space took on urgency. Spitzer eventually got a small telescope into orbit in 1972. But by then he and his young colleague Bahcall were thinking about the more ambitious project described in Spitzer's original paper: a much larger space telescope that would--in theory at least--be able see clearly into the outer reaches of the cosmos.

NASA was interested, but Congress was not. "They rejected the first request for funding to study the idea back in 1974," Spitzer recalls. "So astronomers mounted a letter-writing campaign, and John and I testified, and the funding was finally approved." NASA got the official go-ahead in 1977. In 1983 the telescope was formally named after the astronomer Edwin Hubble, who discovered the expanding universe back in the 1920s.

From the start, the space telescope was designed to be launched from the cargo hold of NASA's new space shuttles--a decision that proved a mixed blessing. The first shuttle had not been launched yet, and as the cost of the shuttle program climbed, so did the cost of launching the Hubble. The telescope's dependence on the shuttle also meant that if launches got backed up, the Hubble likewise got delayed. That was already happening before the Challenger disaster; when the Challenger went down with its seven-person crew in January 1986, the Hubble launch was pushed back even further.

There were scientific drawbacks to using the shuttle as well. Shuttles carry payloads only a few hundred miles above the earth's surface. At that altitude, the glaringly bright home planet fills nearly half the sky. Any decision about the Hubble's targets had to take Earth's always changing position into account, a scheduling nightmare. And since the Hubble took only 90 minutes to orbit the earth, the telescope could focus on a single object for a few minutes at most before Earth obscured it.

But as a shuttle-launched satellite, the railroad-car-size Hubble had some important advantages. It was designed to be serviced in orbit; the plan was to have shuttle astronauts visit the telescope every few years to replace the original cameras, electronics and other equipment with new, better-performing instruments.

As NASA learned in 1990 with the discovery of the flawed mirror, easy access to the Hubble's innards was crucial. Even so, installation of a complex array of corrective mirrors--essentially fitting the Hubble with a set of eyeglasses--was a high-cost ($700 million), high-risk venture, and some astronomers were dubious. "They considered the whole thing to be rather a Rube Goldberg creation," says Spitzer. On top of that, the list of tasks assigned to the astronauts who flew the repair mission--not just installing the new optics, but replacing an outdated camera, two wobbly solar-energy panels and three faulty gyroscopes, among other balky components--seemed too long. "I don't think anyone except the astronauts themselves thought they could complete the mission," says Bahcall.

But complete it they did, in a series of televised space walks that riveted the nation's attention in December 1993. Floating on the verge of a black void, the crew of the shuttle Endeavour checked off one item after another on their impossible list until, in what Bahcall calls a display of "superhuman intelligence and ability," they were done. NASA's badly battered reputation was on the line, but within days the report came in: the images were excellent. "It was hard to believe," Bahcall remembers. "Each instrument worked exactly as it was designed."

Almost immediately thereafter, the dramatic scientific results started rolling in. Among the most significant:

By measuring with unprecedented precision the distance to the distant galaxy M100 (56 million light-years), a team of researchers led by Wendy Freedman of the Carnegie Observatories in Pasadena, California, provided the most accurate yardstick ever for gauging the expansion rate, and thus the age, of the universe. Their illogical preliminary answer: the cosmos is between 8 billion and 12 billion years old--or about 2 billion years younger than the oldest known stars. While Freedman and others refine their measurements, cosmologists are scrambling to patch up their theories. To save the idea of the Big Bang, the postulated explosive event that created the universe, they are even talking of reviving the idea of the cosmological constant--a sort of universal antigravity force that Einstein proposed and then discarded as inelegant.

The growing consensus that gigantic black holes lurk at the core of many galaxies--including our own--was confirmed by Holland Ford, now at Johns Hopkins, and his collaborators, who used the Hubble to spot a superheated disk of gas spinning at a dizzying 1.2 million m.p.h. at the very heart of the galaxy M87, 50 million light-years from Earth. The only reasonable explanation: the gas is funneling, like water down a drain, into the gravitational pit of a black hole as massive as 2 million suns.

Bahcall has used the telescope to take pictures of quasars, starlike objects so bright they can be seen halfway across the universe. Most theorists think quasars are intimately related to giant black holes like the one Ford found; presumably their intense light comes from gas compressed with such force that it explodes in bright bursts of energy. That implies that every quasar should have a galaxy around it, but in several cases Bahcall found no clear evidence of one. "This," he said when he announced his observations, "is a giant leap backward in our understanding of quasars."

Hubble gave planetary astronomers an unprecedented once-in-a-lifetime view of the mountain-size fragments of comet Shoemaker-Levy 9 smashing one after another into Jupiter. While other telescopes picked up the flashes of light generated by the multimegaton impacts, only the space telescope could see details of the scars they left behind. By carefully observing the dark smudges that the fragments stamped into Jupiter's cloudtops, scientists have begun to understand how the giant planet's stormy atmosphere works.

More than a score of astronomers working in several teams have taken the sharpest pictures ever of some of the most distant known galaxies--some as much as 10 billion light-years away--and shaken up the conventional wisdom on galactic evolution. Many theorists believed that spiral galaxies--delicate, pinwheel-shape collections of stars like the Milky Way--were the first to evolve in the universe. Occasionally they'd crash into each other, and the resulting amorphous blob would turn into an elliptical galaxy, the second major class of star system. But what the Hubble showed was that there have been elliptical galaxies almost from the beginning, and that the earliest spirals were gnarled and distorted--not spiral at all. "The day that result came out," says Thompson, "one of my colleagues had to quickly rewrite a lecture he was giving later that afternoon."

INDEED, BEFORE THE HUBBLE IS FINished, all sorts of lectures, textbooks and astronomical theories will have to be rewritten. As Robert Williams, director of the Space Telescope Science Institute, in Baltimore, Maryland, points out: "There's long been a belief that whenever you have a tenfold advance in telescope resolving power, you're going to have unexpected discoveries. The Hubble has confirmed it." Right now, in fact, the telescope is taking pictures of a very distant part of the universe that will probe deeper into the cosmos than anyone ever has. Williams expects to release the images sometime this winter--and promises that they will be worth waiting for.

Also worth waiting for are the improvements that will make the telescope many times more powerful than it is today. Shuttle missions are scheduled to dock at the telescope in 1997, 1999 and 2002, each time upgrading the Hubble's cameras and other instruments. "We're going to be replacing the original 1970s and 1980s technology with 1990s instruments," says Weiler. "It'll essentially be a new telescope." Hubble's official working lifetime ends in 2005, when its guaranteed funding runs out. At that point NASA, the astronomers who use the Hubble, and Congress will have to decide whether to keep refurbishing the aging observatory. It may be that in the next generation of ground-based telescopes, new computerized methods of correcting for atmospheric blur will finally make obsolete the notion of putting a telescope in space to take sharp pictures.

But by then the Hubble will have justified its reputation, and its $5 billion-to-$6 billion overall cost, many times over. "That's about the price of a new aircraft carrier," Weiler points out. Spread out over 25 years, he estimates, it comes to about 2-c- a week for every man, woman and child in the U.S. Says Bahcall: "We can take pride in an achievement that no other nation could even consider. It's like our pyramids--but a whole lot more important." And, to our eyes, even more beautiful.