The Hubble Space Telescope has surprised astronomers by taking a new head count of a stellar "baby boom" in a neighboring galaxy, turning a mere engineering test into the first proof that the orbiting observatory will still be able to make significant findings despite its flawed mirror.
In pictures taken on Aug. 3 and released yesterday, the Hubble shows 60 of what may be the youngest and heaviest known stars -- some of them possibly 100 times as massive as the sun -- clustered in a star cloud known as "30 Doradus" nebula, which lies within the constellation Dorado (The Swordfish), visible in the Southern Hemisphere. The stars appear to be part of a cosmic nursery of newborn stars.
As recently as 10 years ago, astronomers believed the bright spot in 30 Doradus was just one titanic star. New telescope technology in the 1980s enabled them to resolve the fuzzy image into eight stars and the most recent ground telescope images had suggested there might be as many as 27 stars.
The Hubble images -- which were computer-enhanced to remove some of the blurring effects of the telescope's flawed mirror -- double that figure and hold out the promise of new insight on how stars are born, evolve and die, scientists said at a briefing to announce the discovery yesterday.
"We knew we were sitting on a pot of gold," said NASA's Sally Heap, an astrophysicist at Goddard Space Flight Center in Greenbelt, as she described the 2 a.m. excitement when scientists got their first look at the new images.
"We're very encouraged by this," said James Westphal of the California Institute of Technology, principal investigator for the Wide Field/Planetary Camera, the Hubble's workhorse instrument, which took the new images.
Although Westphal's camera team still expects to delay at least 80 percent of their planned work until a new camera is launched and installed aboard the Hubble in 1993, he said, the prospects looked even worse before the new images came in. "It's clear here we can do wondrous good stuff."
"This image is a lot better than we expected a month ago," said Ed Weiler, NASA's chief scientist on the Hubble project.
The new pictures also show clearly the halo effect caused by the flaw in the Hubble's primary mirror. The mistake, now thought to be the result of a fault in an instrument used to guide its manufacture a decade ago, still will curtail or delay many of the Hubble's scientific studies of the heavens.
But the Doradus discovery is the first demonstration that, with computer enhancement, the Hubble's images of bright objects, at least, can be as sharp as or sharper than many scientists had hoped, they said. Future images should be even better as instruments are calibrated, exposures are lengthened and other improvements made, they added.
The cores of the stars as shown in the new images are 10 times as sharp as the average seen from the ground, and five times better than can be obtained on an excellent viewing night on the ground, said astronomer Rick White, of the Space Telescope Science Institute in Baltimore. "The cores are the same size as if the mirror were perfect."
The new images show "that computer restoration is going to be a powerful tool" in efforts to overcome the built-in flaw, he said.
However, he and others noted that computer enhancement will not be as useful in restoring the sharpness of images from fainter, more distant objects. According to Westphal, the Hubble's effectiveness in studying faint objects still will be "ten times worse" than originally planned.
The young stars in Hubble's surprise census are only about 160,000 light years from Earth, located in the Large Magellanic Cloud, where a supernova -- or exploding star -- burst in the southern hemisphere in January 1987, closer to Earth than any in four centuries.
The 60 stars are such babies that they weren't in the heavens seen by ancient civilizations, Weiler said. And they are so tightly packed that they would fit into the empty space between the sun and its nearest star, Alpha Centauri, which is just four light years from Earth.
The Doradus hot spot is so bright that, one American astronomer once stated, if it were put in place of the nearer Orion Nebula it would cast shadows on the nighttime landscape of Earth.
"We now have the finest family portrait of stars outside our galaxy," said Heap, describing the stars as "the hottest, heaviest stars that are known . . . The stars in this cluster define the limits."