The Hubble Space Telescope, which has already yielded stunning new views of the universe, is about to get a make-over.
Tomorrow, astronauts aboard the space shuttle Discovery will begin the first of four spacewalks to outfit the orbiting observatory with two new devices. These devices will enable scientists to look further back into the universe's history than ever, peer through the blankets of dust that cloak the birth of stars, and take the measure of massive black holes.
"This is going to lead to new science, especially [about] the origins of objects," says Rodger Thompson, an astronomer at the University of Arizona at Tucson.
Right now, Hubble's "eyes" are sensitive to visible and ultraviolet light. Orbiting above the distorting effects of Earth's atmosphere, the $2 billion telescope has yielded images of distant galaxies, nebulae, and stellar nurseries of dust and gas that rival anything George Lucas's Industrial Light & Magic could devise.
The expansion of the universe and the dust it contains, however, are taxing Hubble's abilities. The most distant galaxies, whose light has traveled for billions of years, also are the youngest. Scientists are keenly interested in what these galactic infants can tell them about how the universe has evolved. But by the time light from these far-away and fast-receding galaxies hits Earth, it's shifted into infrared wavelengths, which Hubble can't "see."
One new device will extend Hubble's vision into the near infrared. Chilled by a 230-pound block of nitrogen ice, the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) will image galaxies as young as 5 percent of the universe's age, instead of today's limit of about 10 percent.
"This is a critical time," says Dr. Thompson, NICMOS's lead scientist. "We want to know when galaxies became the galaxies we see today. We think it's in this period."
And since infrared light passes through the dust that scatters visible wavelengths, NICMOS is expected to help unlock the secrets of star formation.
"One of the really neat pictures from Hubble was of the star-forming regions," says Robert Kirshner, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. With NICMOS, "we'll be able to see into these and see the stars forming."
He adds that NICMOS could represent "a tremendous step forward" for efforts to use light from certain classes of stars to more precisely measure cosmic distances, which are then used to derive the universe's age.
ASTRONAUTS will also add a device for breaking light into discrete wavelengths, to help researchers analyze everything from an object's chemical composition to its velocity. The Space Telescope Imaging Spectrograph will allow astronomers to take spectra of lots of objects simultaneously, rather than one at a time.
"When we look at the center of galaxies where we think there's a black hole, for example, we look at stars near where we think the black hole is," Dr. Kirshner says. Using the old spectrograph with its single tiny hole to bring in light, astronomers could look at only one point at a time near the black-hole candidate. The new device, he says, will look at a slice of space across the candidate and see how quickly a large number of stars are spiraling toward it - data that can verify the black hole's presence and be used to estimate its mass.
Kirshner notes that unlike the 1993 mission that corrected Hubble's flawed vision, "we have a lot to lose this time if something goes wrong or if one of the new instruments is a dud." Yet, he adds, to him and other astronomers worldwide using Hubble data, the potential payoff is worth the risk.