When the powerful new Hubble Space Telescope was launched in 1990, astronomers predicted that it would upset a lot of theoretical apple carts on its way to new discoveries.
Three new reports from Hubble astronomers, including one described as "revolutionary," have proven those forecasts correct.
The discoveries are challenging previous theories relating to gravitational "lenses," intergalactic hydrogen clouds and the chemistry of the early universe. Hubble's contributions to the debate were discussed yesterday at the 179th meeting of the American Astronomical Society in Atlanta.
In the first Hubble report, a "snapshot" survey of 300 distant quasars has found only one whose light appears to be bent and split into multiple images by the intense gravity of intervening matter.
These split images of bright quasars are a valuable tool for astronomers working to find out how much invisible "dark matter" exists in the universe.
Ground telescopes already had found about a dozen examples of such "gravitational lensing," and some scientists had predicted at least that many more would be detectable by sharper-eyed space telescopes.
But Hubble's findings may indicate new limits on dark matter, and they "already rule out some of the extreme theories," says John Bachall of the Institute for Advanced Study in Princeton, N.J.
Bachall was assisted by scientists from the Space Telescope Science Institute in Baltimore and the Institute for Astronomy in Cambridge, England.
In another study, scientists looking at deep-space hydrogen clouds using Hubble's Faint Object and High Resolution spectrographs have found that the closer clouds are not as randomly spaced as had been thought. Many of them now appear to be directly associated with individual galaxies, or clusters of galaxies.
"This is a revolutionary finding, if supported by future observations," says Bachall. "We would have never thought of looking for this explanation if it hadn't kicked us in the face."
The clouds themselves are invisible, and must be observed by measuring the frequencies of energy they absorb and subtract from the light of much more distant quasars shining through them. It's a little like observing a chick embryo by shining a bright light through the egg.
Unfortunately, when relatively nearby hydrogen clouds are the target, those light frequencies are found in the ultraviolet bands of the spectrum, which is blocked by Earth's atmosphere. Until Hubble's launch, they were inaccessible to astronomers.
Finally, scientists from the Space Telescope Science Institute and from the University of Texas in Austin have been surprised by evidence of boron in a Hubble spectrograph of light from an ancient star only 100 light years away in the Libra constellation.
Boron and another light element, beryllium, might have been formed by cosmic rays during the birth of the Milky Way Galaxy, scientists say, but not in the exact proportions found by Hubble.
That opens the possibility that this boron may have been created billions of years earlier, just after the Big Bang. That, scientists say, would lend support to new theories that the universe immediately after the Big Bang was not as uniformly hot and dense as once thought.
The competing theories will be tested later this year as astronomers use Hubble to look for boron in an even older star. If the boron was created by cosmic rays in the young Milky Way, there should be less of it in an older star. If all the boron was created in the Big Bang billions of years before, the amounts found in the stars should be the same.
"Either way, this will be an exciting test," says Douglas Duncan, of the Space Telescope Science Institute. "Our picture of the beginning of the galaxy and the beginning of the universe is undoubtedly oversimplified, and it is satisfying to be able to add a little more detail."
More discoveries by scientists working with the Hubble Space Telescope are expected to be announced later this week at the AAS meeting in Atlanta.
Hubble scientists have been making their observations despite a manufacturing error that distorted the space telescope's 1,800-pound, 8-foot primary mirror, and persistent vibrations and pointing system failures.