This electronic version of NASA News Release 99-65 
incorporates a correction made after the news release was 
issued.




Donald Savage 
Headquarters, Washington, DC                 May 25, 1999
(Phone:  202/358-1547) 

Nancy Neal 
Goddard Space Flight Center, Greenbelt, MD 
(Phone:  301/286-0039) 

Ray Villard 
Space Telescope Science Institute, Baltimore, MD 
(Phone:  410/338-4514) 

RELEASE:  99-65

HUBBLE COMPLETES EIGHT-YEAR EFFORT 
TO MEASURE EXPANDING UNIVERSE

       The Hubble Space Telescope Key Project Team today 
announced that it has completed efforts to measure precise 
distances to far-flung galaxies, an essential ingredient 
needed to determine the age, size and fate of the universe.

       "Before Hubble, astronomers could not decide if the 
universe was 10 billion or 20 billion years old," said team 
leader Wendy Freedman of the Observatories of the Carnegie 
Institution of Washington.  "The size scale of the universe 
had a range so vast that it didn't allow astronomers to 
confront with any certainty many of the most basic questions 
about the origin and eventual fate of the cosmos.  After all 
these years, we are finally entering an era of precision 
cosmology.  Now we can more reliably address the broader 
picture of the universe's origin, evolution and destiny."

       The team's precise measurements are the key to 
learning about the universe's rate of expansion, called 
Hubble's constant.  Measuring Hubble's constant was one of 
the three major goals for NASA's Hubble Space Telescope when 
it was launched in 1990.

       For the past 70 years astronomers have sought a 
precise measurement of Hubble's constant, ever since 
astronomer Edwin Hubble realized that galaxies were rushing 
away from each other at a rate proportional to their 
distance, i.e. the farther away, the faster the recession.  
For many years, right up until the launch of the Hubble 
telescope -- the range of measured values for the expansion 
rate was from 50 to 100 kilometers per second per megaparsec 
(a megaparsec, or mpc, is 3.26 million light years).

       The team measured Hubble's constant at 70 km/sec/mpc, 
with an uncertainty of 10 percent.  This means that a galaxy 
appears to be moving 160,000 miles per hour faster for every 
3.3 million light-years away from Earth. 

       "The truth is out there, and we will find it," said 
Dr. Robert Kirshner of Harvard University.  "We used to 
disagree by a factor of two; now we are just as passionate 
about ten percent.  A factor of two is like being unsure if 
you have one foot or two.  Ten percent is like arguing about 
one toe. It's a big step forward."  Added Robert Kennicutt of 
the University of Arizona, a co-leader of the team:  "Things 
are beginning to add up. The factor-of-two controversy is 
over."

       The team used the Hubble telescope to observe 18 
galaxies out to 65 million light-years.  They discovered 
almost 800 Cepheid variable stars, a special class of 
pulsating star used for accurate distance measurement.  
Although Cepheids are rare, they provide a very reliable 
"standard candle" for estimating intergalactic distances.  
The team used the stars to calibrate many different methods 
for measuring distances.

       "Our results are a legacy from the Hubble telescope 
that will be used in a variety of future research," said 
Jeremy Mould of the Australian National University, also a 
co-leader of the team.  "It's exciting to see the different 
methods of measuring galaxy distances converge, calibrated by 
the Hubble Space Telescope."

       Combining Hubble's constant measurement with estimates 
for the density of the universe, the team determined that the 
universe is approximately 12 billion years old -- similar to 
the oldest stars.  This discovery clears up a nagging paradox 
that arose from previous age estimates.  The researchers 
emphasize that the age estimate holds true if the universe is 
below the so-called 'critical density' where it is delicately 
balanced between expanding forever or collapsing.  
Alternatively, the universe is pervaded by a mysterious 'dark 
force' pushing the galaxies farther apart, in which case the 
Hubble measurements point to an even older universe.

       The universe's age is calculated using the expansion 
rate from precise distance measurements, and the calculated 
age is refined based on whether the universe appears to be 
accelerating or decelerating, given the amount of matter 
observed in space.  A rapid expansion rate indicates the 
universe did not require as much time to reach its present 
size, and so it is younger than if it were expanding more 
slowly.

       The Hubble Space Telescope Key Project Team is an 
international group of 27 astronomers from 13 different U.S. 
and international institutions.  The Space Telescope Science 
Institute is operated by the Association of Universities for 
Research in Astronomy, Inc. for NASA, under contract with 
NASA's Goddard Space Flight Center, Greenbelt, MD.

                          - end -

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