Today, the Hubble Space Telescope turns 10 years old, and as astronomers pause to celebrate a decade of unprecedented discovery, they look forward to a second decade of even more spectacular observations.
Three astronaut-service missions - especially last December's repairs - have prepared the orbiting observatory to pursue knowledge that was beyond the reach of its original designers.
Past upgrades, and two more planned for 2001 and 2003, are giving astronomers what "in many respects will be a new telescope," says Mario Libio, an astrophysicist at the Space Telescope Science Institute in Baltimore, which manages the Hubble program. "We will have a front-row seat" as the observatory "sees things that happened very early ... perhaps when the universe was only 1 percent of its present age."
Beginnings of the cosmos
Astrophysicists have worked out plausible theories as to how the cosmos evolved when it was that young. Now those theories will be tested as the reborn space telescope sees farther into space and farther back in time than any telescope has seen before. However, its findings will be interpreted in the light of what astronomers generally consider one of the most fruitful decades in the history of their science.
"Not since Galileo aimed a small ... telescope into the night sky in 1609 has humanity's vision of the universe been so revolutionized in such a short time span by a single instrument," says David Leckrone, Hubble project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md.
When it was launched on April 24, 1990, one of the Hubble's primary goals was to narrow the estimate of the universe's age. It's done that - putting the age at 12 billion to 14 billion years.
Now, "we're moving from studying the age of the universe to studying its evolution," says Lewis Hobbs, an astronomer at the University of Chicago.
Among the observatory's other accomplishments:
*Definitive evidence of black holes: These are objects so dense that nothing can escape their gravity - not even light. Dr. Hobbs calls this evidence "very important" in understanding what goes on in the center of galaxies, many of which have black holes.
*The Hubble's so-called "deep field" images show a myriad of galaxies at an early stage of the universe. Hobbs says "those studies are just so fundamental" in understanding galaxies. Now the telescope will look at even earlier stages.
*Gravitational lensing: The gravity of massive galaxies can act like lenses to form images of more-distant objects behind them. Hubble has found so many of these lenses that astronomers now are starting to use them to study very distant parts of the cosmos.
*Circumstellar disks have been detected around young stars in the Orion Nebula. The images showed for the first time that such disks of dust and gas, from which planets might form, are common in stellar nurseries.
*Brown dwarf star detection: These bodies, which are a bit too small to form full-blown stars, had been hard to spot. Hubble instruments have played what Hobbs calls "a historically important supporting role" in locating them.
NASA sums up the record by noting that the 12.5-ton observatory found 13,670 objects and made 271,000 individual observations in its first decade.
Such success once seemed elusive. When controllers turned on the Hubble instruments a decade ago, they saw blurred images. As NASA now wryly observes, the main telescope mirror "was expertly made, but to the wrong prescription."
Preplanned servicing has been the project's saving grace. During the first mission in 1993, astronauts fitted "eye glasses" that restored the telescope's sharp vision. Servicing in 1997 and 1999 repaired damage, replaced failed parts, and installed new instruments.
The observatory now is half way through its planned life.
In 2010, NASA's Next Generation Telescope (NGT) will replace it, according to the current plan. It will have a mirror several times larger than the 7.9-foot Hubble dish.
Its main goal will be to look far deeper into the universe than the Hubble, using infrared light, which penetrates intervening dust.
This time, the manufacturer has to get the hardware right. The NGT will be placed 1 million miles from Earth on the side away from the sun. That's beyond the reach of any foreseeable servicing mission.
For the general public, the Hubble epoch is a unique scientific adventure. People everywhere have - and will continue to have - the opportunity to share the telescope's discoveries with scientists week after week as new images come in. News media regularly publish them. Anyone with internet access can view and download them.
(c) Copyright 2000. The Christian Science Publishing Society