Hubble at 15 still unmatched

In the Stars: Hubble at 15 still unmatched


By Phil Berardelli
UNITED PRESS INTERNATIONAL


Washington, DC, Apr. 25 (UPI) -- A spectacular new era in astronomy
began on April 25, 1990, although it took most of the world a while to
appreciate the magnitude of the change.


On that date, the Hubble Space Telescope, launched by NASA the previous
day, first opened its eyes to the heavens. Despite its ungainly
appearance -- the schoolbus-sized spacecraft looks like a tall aluminum
beer can stacked atop a delabeled large-sized can of tomato sauce and
flanked by twin solar panels -- the $1.5 billion instrument carried the
most advanced astronomical equipment available to begin a
two-decade-long mission of probing the heavens more deeply than ever
before.

At least, that was the original plan.

It turned out, however, that despite years of planning and testing, the
telescope's designers and builders had let Hubble fly carrying a major
flaw: Its primary mirror was out of focus, so the first images returned
to Earth were, to put it mildly, disappointing.

It took a daring repair mission mounted by the crew of the space
shuttle Endeavour between Dec. 5-9, 1993, to correct Hubble's problem.
The mission -- the first of four over the years -- required five space
walks totaling nearly 35 1/2 hours, but it gave the telescope the
visual acuity its designers had intended. Very soon, the 12-ton
telescope began reclassifying as obsolete all previous concepts of what
observations of the night sky should produce.

In image after stunning image, Hubble gave human observers a look at
previously unknown places: clouds of gas back-lit by the heat and light
of supernovae, giant spiral galaxies mated with smaller companions,
galaxies in the process of collision, galaxies of unusual shape,
illuminated clouds astronomers identified as the hatcheries of young
stars.

Nearer to Earth, Hubble photographed the planets of the solar system
with unparalleled clarity, bringing a red Mars, massive Jupiter, ringed
Saturn and canted Uranus into razor-sharp focus. Hubble even managed to
capture a cataclysmic event when the 21 fragments of Comet
Shoemaker-Levy plowed into Jupiter's cloud tops over the course of a
week starting July 16, 1994.

Maybe the most famous image of all turned out to be due to the
marketing sense of the Hubble team's scientists. In November 1995, the
telescope's Wide Field and Planetary Camera 2 captured a striking
nebula -- cataloged as M16, but called Eagle -- in a relatively nearby
region of the Milky Way called Eagle, about 6,500 light-years away in
the constellation Serpens.

For the first time, Hubble's image allowed astronomers to view a
phenomenon called evaporating gaseous globules, or EGGs -- dense,
compact pockets of interstellar gas in the process of forming stars.

No doubt it was valuable scientifically.

"For a long time astronomers have speculated about what processes
control the sizes of stars -- about why stars are the sizes that they
are," Jeff Hester, of Arizona State University in Tempe and an image
team member, said at the time. "Now in M16 we seem to be watching at
least one such process at work right in front of our eyes."

The real sensation, however, arose because the Hubble team took the
image, which originally appeared downward, and reversed its
orientation, then named it the "Pillars of Creation."

Instead of bright regions lurking below long and ominous-appearing
tendrils of gas, and resembling stalactites with glowing tips, the
image released to the public suggested something grand and majestic --
halos protruding from monstrous columns light-years in length.

"This is the first time that we have actually seen the process of
forming stars," Hester said.

The Eagle Nebula image quickly became one of the most popular and
recognizable images of astronomy. It presented something truly awesome,
suggesting the universe could be full of such inspiring sites.

Though less dramatic visually, Hubble's greatest achievement so far is
the image captured in late 2004 by its Ultra-Deep Field camera. An
exposure requiring 1 million seconds and focusing on an ostensibly
empty area of the sky near the constellation Orion, the image probed
more deeply into space and the past than anything ever attempted before
-- about 12 billion light years.

There are about 10,000 objects in the UDF image, and each one is a
galaxy. The implication is inescapable: This relatively tiny, seemingly
empty patch of the night sky is teeming with galaxies, each containing
at least tens of billions of stars.

The sad news about Hubble's odyssey is it probably is going to end
soon. Of the six gyroscopes the spacecraft carries to enable it to
focus on a fixed point in the sky, three have shut down. Hubble can
continue to perform its mission with the three remaining units, but if
one more gyroscope fails, it will lose its ability to maintain the
quality of its images.

NASA had commissioned a fifth shuttle servicing mission to Hubble, but
canceled it after the Columbia disaster in February 2003. Now, Michael
Griffin, the agency's new head, is attempting to decide whether to risk
that mission to extend the telescope's operational lifetime. What
Griffin decides could affect the state of visible-light astronomy
perhaps for decades, because as of now, there is no immediate
replacement for Hubble. Its place in the history of science seems, for
the moment -- and sadly -- unique.


In the Stars is a series examining new discoveries about the cosmos, by
Phil Berardelli, UPI's Science & Technology Editor. E-mail: