Hubble's Stellar Images

With shades of yellow, orange, and blue -- and ever-dwindling shades of dollar-bill green -- astronomers are using the Hubble Space Telescope to paint breathtaking pictures of the universe.

In the year since the shuttle Endeavour and its crew salvaged Hubble, the $1.5 billion orbiting observatory has been giving humanity an unprecedented look at the heavens, peering ever deeper into the past and providing scientists who try to explain the cosmos with more questions than answers.

With new instruments scheduled to be added in 1997, the telescope is expected to push the limits of the observable universe out even farther.

''I'm trying to think of how to phrase this without sounding hyperbolic, but this has been the most spectacular year in my professional career,'' says David Leckrone, the Space Telescope's senior project scientist at the National Aeronautics and Space Administration's (NASA's) Goddard Space Flight Center in Greenbelt, Md.

''There certainly is much more excitement now than there was a year ago,'' agrees Boston University astronomer Ken Janes.

In December 1993, the world watched with fascination as shuttle astronauts danced a delicate minuet with the bus-sized observatory. Placed in orbit in April 1990, it was to be one of the cornerstones of NASA's ''Great Observatories'' series of astronomical satellites. It had been billed as the telescope that would gaze with exceptional clarity from above the atmosphere to the very edge of the known universe. It was to help answer the most basic questions: How old is the universe, and what is its future?

What is it made of? How do galaxies, the universe's basic building blocks, evolve? Are there other planets around other stars? Can we observe black holes?

Hubble Telescope Finds Redemption in the Stars

Initial images of a star cluster that was 1,260 light years away seemed to be harbingers of discoveries to come: The image quality was said to be 10 times better than Earth-bound telescopes could deliver. But two months after the shuttle delivered Hubble to space, engineers trying to align the telescope discovered a significant flaw in its mirror that sent hopes plummeting. Subsequent investigations found fault with NASA's oversight and management. Meanwhile, ground-based telescopes were being planned t o take advantage of new technologies to compensate for the blurring effects of Earth's atmosphere -- approaching, at least on paper, some of Hubble's capabilities for roughly a tenth of Hubble's cost.

By August 1990 hopes began to rise again as astronomers reported views of the core of Galaxy NGC 7457, again, with 10 times the quality of ground-based observations. The mirror's flaw had its greatest impact on Hubble's ability to resolve very faint objects, such as very distant, early galaxies.

Astronomers were further encouraged in 1992 as Hubble images allowed them to study candidates for black holes and to make observations that would allow them to refine distance measurements that in turn could be used to refine estimates of the age of the universe.

Meanwhile, NASA had begun planning the repair mission, which would replace the wide-field and planetary camera with one using newer technology and corrective lenses, as well as give three other critical instruments ''glasses'' to compensate for the mirror's flaw.

On that mission, ''manned and unmanned spaceflight came together,'' Dr. Leckrone says. ''The mission itself went splendidly. We began getting images four to five weeks earlier than expected.'' And the performance of the refurbished Hubble exceed even the original design specifications, he says.

The mission ''blew me away,'' agrees Anne Kinney, an astronomer and director of educational programs with the Space Telescope Science Institute (STScI) in Baltimore. ''I would have been delighted if it had been 75 percent successful, but it was 100 percent successful.''

Hubble has been blowing astronomers away ever since -- in large part because it now is able to make the observations that drove its construction.

The latest were released Dec. 6, when three teams, led by astronomers from the Carnegie Observatories in Pasadena, Calif. and the STScI, released three childhood photos of the universe, the oldest dating as far back as 2 billion years after the Big Bang, or 10 to 15 percent of the universe's current age.

One surprise: seeing fully formed elliptical galaxies at each stage. ''This opens up a whole can of worms,'' says Alan Dressler, an astronomer from the Carnegie Observatories and one of the team leaders. That such aged galaxies are seen at such early points in the universe's history -- even at the 2 billion-year-old mark -- may throw yet another wrinkle into trying to pin down the age and expansion rate of the universe.

The images also give intriguing looks at the evolution of galaxies. While elliptical galaxies appear fully formed at each point, ''the evidence for spiral galaxies is very chaotic,'' says Bruce Margon, chairman of the astronomy department at the University of Washington.

''We know that today spirals are the most common type of galaxy, yet very few appear in clusters,'' Dr. Dressler says. ''When we look back 5 billion to 10 billion years, we see great big spirals in clusters, but we also see twisty shreds. The spirals tend to be more irregular and ragged. They either could be more juvenile or perhaps they are being torn apart.''

Mark Dickinson, an astronomer at the STScI and another team leader, adds, ''There is a tremendous menagerie of shapes that have no counterpart in today's universe.''

Until now, the ability to identify points at which the early universe looked different from today's has eluded astronomers, Dr. Margon says, adding, ''What we're seeing is marvelously complex.''

Among the year's other major observations:

* Images of a pair of illuminated rings near a supernova that appeared in 1987 in the Large Magellanic Cloud, a companion to the Milky Way. Although the rings could also be seen with ground-based telescopes, the images weren't clear enough to allow scientists to interpret what they saw. One explanation: narrow jets of hot matter and radiation from either a black hole or a neutron star, acting on the gas ejected by the supernova's precursor star. Whatever the object is, ''it is unprecedented and bizarr e,'' says Chris Burrows, an astronomer with the European Space Agency and STScI . ''We have never seen anything like this before.''

* Clear images of large disks of dust swirling around newly forming stars in the Orion Nebula, representing ''the most direct evidence to date for protoplanetary disks,'' according to C. Robert O'Dell, an astronomer at Rice University and one of two researchers who made the observations. His finding reinforces the notion that planet formation is a common process, raising the prospects for life elsewhere in the galaxy.

* The most accurate measurements at the farthest distance to date of a class of stars called Cephid variables. These stars have served as ''standard candles'' for determining distances in the universe. The Cephids were observed in a galaxy, designated M100, that is part of a cluster in the constellation Virgo. When the new distance (56 million light-years) is plugged into calculations of the universe's expansion rate, the galaxy is moving away from the Milky Way at 60,000 miles an hour. The finding also

bears on efforts to pin a more precise age on the universe, which require knowing the expansion rate, or Hubble Constant, and the density of matter in the universe. The finding implies an age for the universe of 8 billion to 12 billion years, which would make the universe younger than some of the oldest stars in the Milky Way -- or some of the oldest elliptical galaxies reported in last week's results on the early universe.

* In what Dr. Leckrone calls ''a once-in-a-millenium opportunity,'' Hubble recorded a comet's collision with Jupiter. The comet, Shoemaker-Levy 9, broke into several pieces as it approached the giant planet in July. As the fragments plunged into Jupiter, astronomers gained new insights into Jupiter's magnetic field, the circulation patterns of winds below the cloud tops, and the composition of the comet itself.

Planners hope to build on these discoveries as they look ahead to 1997, when the shuttle is scheduled to visit Hubble to replace three instruments and refurbish the satellite.

One instrument, a new $90 million spectrograph -- which not only helps determine the chemical compositions of what it sees but also helps determine direction and speed of motion -- is designed to allow observations across a wider field of view than the existing spectrograph. ''It's now awkward to get spectra of the centers of elliptical galaxies and their immediate environments at the same time,'' says Chris Blades, head of the office at Goddard that is preparing for the 1997 shuttle mission. ''If you'r e studying black holes, the new instrument will record the nucleus and its environment simultaneously. It also will be more effective at detecting very faint objects.'' The one device will replace two older spectrographs now on the telescope.

The other instrument will improve Hubble's ability to see infrared images. This is of particular interest to astronomers studying very distant galaxies. The more distant the galaxy, the faster it travels away from Earth. Just as a train horn rises and falls in pitch as it approaches and passes a listener, so light shifts toward the blue end of the light spectrum if it is approaching and toward the red when it is receding. The new near-infrared camera ''will allow us to see galaxies even further away as

their light shifts to red,'' Dressler says.

Beyond 1997, however, plans for Hubble get murky. Tight budgets generally and plans for new projects at NASA are tightening the screws on the program, says Ed Weiler, Hubble's program scientist at NASA. ''Our budget's been cut three times over the last three years, even this year, despite the successful repair mission.

In 1999, the shuttle is scheduled to return to the telescope, whose orbit is slowly decaying. The shuttle will move it back into a higher orbit, and the crew will install a new advanced camera on the observatory. But budgets are constraining what NASA can do, says Dr. Weiler: ''Two years ago, we were thinking about a $100 million instrument; now we may have to do it for $25 million.''

Two weeks ago, a committee completed its review of candidates for the 1999 instrument and sent its list of priorities to NASA for review. The agency is expected to pick the design next month. While declining to give details of specific proposals, Dr. Blades, who was on the committee says, ''We can't build it for $25 million.'' He anticipates a $40 million price tag, with some of the extra money coming from other sources.

Looking even farther out, calls are scheduled to go out soon for proposals to replace some instruments in 2002. In addition, a panel of astronomers has been looking at potential follow-ons to Hubble, which has a 15-year design life, after 2010. ''We've agreed that you want to take a leap,'' says Weiler, not just put up another, higher-tech Hubble. One concept: a constellation of five or six one-meter telescopes spread out over a large distance. Their images would be combined using a technique known as interferometry to deliver vast improvements in the ability to separate distant, closely spaced objects that now may appear as one fuzzy blob. ''It would be like being able to spot a fly on Jupiter,'' he says.

Hubble's successes in 1994 have not obscured the views of some astronomers who maintain that while the observatory is an asset, it still was not the best way to conduct space research.

''This may be hindsight, but the program was never really done right,'' says Boston University's Dr. Janes, who is working with a group that is using Hubble to study globular clusters. ''NASA wanted one magnificent instrument that could do everything. It got so extraordinarily complicated and expensive. So many things could have gone wrong and did. We could have gotten more and better science for less money using smaller projects.''

But acknowledging budgetary politics, he notes that ''smaller projects are easier to chop. It's the Hubble type of things that tend to go on.''

Indeed, the seemingly unending string of well-publicized discoveries this year could raise questions about whether the effort has been orchestrated for maximum impact on a tight-fisted Congress.

''No,'' replies one congressional staff member who has followed the space program closely for years. ''These are being driven by the science. This truly is a redemption story.''