Gauging the Age of the Universe / Hubble research team: 12 billion
years old

By Earl Lane. WASHINGTON BUREAU


        Washington  -  Culminating eight years of measurements with the
Hubble Space Telescope, a research team said yesterday it had determined
the expansion rate of the universe with 90 percent accuracy and had
estimated its age to be about 12 billion years.
    NASA officials said the team's precise measurement of the so-called
Hubble constant is a significant advance and was one of the major goals
for the space telescope when it was launched in 1990.
    "One of the prime rationales for starting the construction of the
Hubble was an accurate determination of this constant," said Edward
Weiler, NASA Associate Administrator for Space Science.
    Measuring the expansion rate of the universe  -  on which there has
been heated scientific debate for decades  -  is of more than academic
interest. On the outcome hinges such fundamental issues as the age, size
and ultimate fate of the cosmos.
    "There are lots of things at stake here," said astronomer Robert
Kirshner of Harvard University. "It's not just a number."
    Allan Sandage, an astronomer at the Carnegie Observatories in
Pasadena, Calif., who long has been been trying to nail down the Hubble
constant, quickly challenged the NASA announcement. "If NASA is saying
this is the end of the road, that is not correct," Sandage said in a
telephone interview.
    The constant is named for American astronomer Edwin Hubble, who
first reported in 1929 that the universe is expanding. He determined
that the farther away a galaxy, the faster it is moving.
  The research team, led by Wendy Freedman of the Carnegie
Observatories, used the Hubble Space Telescope to measure distances to
18 galaxies containing pulsating stars called Cepheid variables. By
watching the pulse rates, astronomers determine intrinsic brightness
and, in turn, how distant the stars are.
    Using Cepheid variables and other measures, Freedman team's
calculated that the current expansion rate of the universe is 70
kilometers per second per megaparsec. That means a galaxy appears to be
moving about 160,000 mph faster for every 3.26 million light years away
from Earth.
    The expansion rate, when combined with an estimate on the density of
matter in the universe, can be used to calculate the age of the cosmos.
As recently as a decade ago, astronomers said, estimates of the Hubble
constant had varied by a factor of two and provoked heated debates on
the age of the universe.
    In 1994, Freedman's team, using preliminary data, had estimated an
age as low as 8 billion years, triggering what came to be called the
"age crisis" because some stars in the universe had been dated as older
than that. How could a universe be younger than its oldest objects?
    The team's new estimate of 12 billion years is consistent with the
age of the oldest stars, according to cosmologist Michael Turner of the
University of Chicago. Freedman said the age estimate is conservative
and could go higher if recent hints  that the universe is pervaded by a
mysterious force pushing the galaxies apart at an accelerating pace are
confirmed.
     Kirshner, who heads another team studying the Hubble constant, said
various estimates are starting to overlap. "What was once a very big
disagreement is now narrowing down," Kirshner said.
    Sandage said his team's best estimate for the constant  -  based on
using certain types of exploding stars called supernovae as distance
yardsticks  -  is 58 kilometers per second per megaparsec, plus or minus
2. "It is not correct that the two values overlap and that the two
groups [his and Freedman's] are in agreement," Sandage said.


Copyright 1999, Newsday Inc.

Gauging the Age of the Universe / Hubble research team: 12 billion years old., pp A26.