For astronomers, the Hubble Space Telescope is more than a space-age tool of their trade. Scientists who use it consider it a symbol of human achievement that unites them with people everywhere.
Astrophysicist John Bahcall at the Institute for Advanced Study in Princeton, N.J., says he looks forward to the next servicing mission of the orbiting observatory, scheduled to launch today, "not as a scientist, but as a proud American."
Hubble astronomer Steven Maran at the Goddard Space Flight Center in Greenbelt, Md., observes that the Hubble represents "one of the greatest lows ... and then one of the greatest highs" of space science. Orbited in April 1990, the 12.5 ton, $2 billion instrument broke the hearts of scientists and laymen alike when its vision turned out to be blurred by an optical fault called spherical aberration.
That vision cleared when astronauts installed corrective "eyeglasses" during the first servicing mission in December 1993. Dr. Maran notes that, since then, the Hubble "has revolutionized most areas of modern astrophysics." This is "something our generation can be proud of," Dr. Bahcall says.
A sampling of images typical of the cosmic views the telescope provides is shown here. The impact of those views is felt in research fields as diverse as solar-system study (where the Hubble had not been expected to excel) and galaxy formation in the early universe. The telescope has imaged a nursery where stars are born and has revealed the presence of planets in other star systems.
For all this new knowledge, mysteries remain for a refurbished Hubble telescope to investigate, says the Space Telescope Science Institute in Baltimore. They include:
* Why does the Hubble-derived age of the universe seem younger than the oldest stars?
* Why did early galaxies have a wider variety of shapes than is seen today?
* How do dying stars create complex, gaseous structures with loops, disks, and comet-like objects that astronomers had not expected?
Astronomer Maran points out that the Hubble perspective has also provided a kind of public service. He explains that "only Hubble saw the actual fireballs lifting off the surface" when comet Shoemaker-Levy struck Jupiter in July 1994. That, he says, gave the public "some appreciation" of a "rare but potentially dangerous" risk of a comet hitting Earth.
Bahcall adds that, while the Hubble has revolutionized astronomical science, it has also changed the way astronomers do their work. Where astronomers once tended to work within specialties and with their own types of instruments, now "you can't find anybody who doesn't have something to do with the space telescope."
Now, specialists work together, pooling their insights. Bahcall says that never again will astronomers work in the isolation of specialties while they try to understand the universe as a complex, vibrant whole.
Astronomers have more than the Hubble to support this holistic exploration. Ground-based observatories and other space-probing satellites often coordinate their work with Hubble studies. Also, the space telescope should soon have a powerful new partner.
Japan is scheduled to launch a 26-foot-diameter orbiting radio telescope this week that will complement Hubble's deep-space observing capability. By combining its data with data taken simultaneously by ground-based radio observatories, astronomers can simulate the observing power of a radio telescope more than 2-1/2 times the diameter of Earth.
This system - a joint project of Australia, Canada, Europe, Japan, and the United States - should have 1,000 times the resolving power of Hubble. From Los Angeles, it could see a grain of rice in Tokyo. This powerful vision at radio wavelengths will allow astronomers to dig into the details of black holes, remote galaxies, and other distant objects that Hubble's optical and infrared images bring to their attention.
An Impressive List of 'Firsts'
Hubble's achievements, documented by the Space Telescope Science Institute in Baltimore, include the following 'firsts':
* Deepest visible look back in time.
* First clear optical images of the most energetic objects known, called quasars.
* Discovery of a natural ultraviolet laser in space.
* First surface map of distant Pluto.
* Discovery of intergalactic helium left over from the big-bang birth of the universe.
The institute also notes that Hubble data have led to astronomically historic conclusions such as the following:
* Theoretical objects called black holes, from which not even light can escape, are real.
* First stages of planet formation are common among stars.
* Jupiter's moon Europa has an unsuspected thin oxygen atmosphere.
* A suspected belt of hundreds of millions of comets encircling the solar system really exists.