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LATEST CALCULATIONS ON AGE OF UNIVERSE STIR BANG-UP DEBATE By Paul Recer Associated Press May 26, 1999
WASHINGTON --
Precise measurements of the distance to certain stars suggests the universe
is about 12 billion years old, somewhat younger than earlier estimates, a team
of NASA astronomers announced Tuesday.
Other experts, however, immediately said NASA's results are in error and
that a solution to one of the basic questions in astronomy is still unknown.
A team of 27 astronomers funded by NASA and led by Wendy Freedman of the
Carnegie Institute of Washington announced completion of an eight-year effort
to measure the distance to 800 special stars in order to calculate the speed
at which all of the galaxies in the universe are moving apart.
Calculating separation speed, called the Hubble constant, was a top
priority of NASA's space telescope because the result is a critical factor in
determining the age of the universe, Freedman said Tuesday at a news
conference.
Freedman said the Hubble constant was determined to an accuracy of 10
percent and when this value is combined with other measurements, it gives an
estimated age of the universe of about 12 billion years.
This number may rise slightly to perhaps 13 1/2 billion years, she said, if
assumptions about the amount of matter in the universe change with further
study.
NASA's announcement was quickly denounced by Allan Sandage, a noted
astronomer and head of a Carnegie Observatories team in Pasadena, Calif., that
has searched for the Hubble constant since 1968.
"If NASA is giving the impression that the problem is solved, then we would
dispute that," Sandage said. "They have announced a final number and they are
not correct."
Astronomers have been searching for the Hubble constant since 1929 when
astronomer Edwin Hubble first found that distant galaxies are moving away from
the Earth faster than are nearby galaxies. Astronomers express the Hubble
constant by measuring the acceleration rate for every 3.26 million light-years
in distance.
Freedman said new measurements taken with the Hubble Space Telescope have
refined the acceleration rate to 70 kilometers per second. This means that a
galaxy is moving away from us 160,000 m.p.h. faster for every 3.26 light-years
in distance from Earth. Freedman said her team's figure was accurate within 10
percent.
Sandage said NASA's new number is still too high.
"We've said all along that the correct number is about 55," he said. This
would give an age of the universe of 14 to 18 billion years, depending on what
is assumed about the mass in the universe, Sandage said.
The expanding universe supports the Big Bang theory, the idea that the
universe began when all matter was compressed into a single point that then
exploded. The theory states that the universe has been expanding ever since.
Recent studies also have shown that the universe probably will expand
forever. Some researchers also believe the expansion is speeding up due to a
force that accelerates matter. Existence of this force is still controversial.
The NASA team reached their Hubble constant number by measuring the
distance to a type of star, called a Cepheid, that pulsates at a known rate
and strength. By measuring Cepheids in 18 galaxies out to 65 million
light-years, said Freedman, the team established the rate of expansion.
Sandage said his team measured distances to nine star explosions, called
supernovae, and then confirmed these distances with Cepheid measurements. He
said this method is more accurate.
Both teams used the Hubble Space Telescope which can study stellar detail
that is unseen by ground telescopes.
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