ROANOKE TIMES
Copyright (c) 1996, Roanoke Times
DATE: Friday, May 10, 1996 TAG: 9605100060
SECTION: NATIONAL/INTERNATIONAL PAGE: A-5 EDITION: METRO
DATELINE: WASHINGTON
SOURCE: Associated Press
Competing teams using different methods of estimating the age of the universe are moving closer to a common figure, though they remain separated by billions of years.
In what was called a ``midterm report'' on a three-year project, astronomers reported at a news conference Thursday that one team has found a universe age of 9 billion to 12 billion years, while the estimate for a second team is 11 billion to 15 billion years.
The calculations are based on values that have changed in recent months by about 10 percent for each group because of added observations.
A team led by Wendy Freedman of Carnegie Observatories in Pasadena, Calif., is using the Hubble Space Telescope to measure the distance to specific galaxies that contain stars called Cepheid variables. These stars pulsate at a cycle that is related to their brightness; this brightness, in turn, can be used to measure distance.
Calculations from these studies put the age of the universe at 9 billion to 12 billion years.
The Freedman team also is using five secondary scales to systematically double-check the Cepheid measurements. So far, the group has analyzed 12 galaxies and expects to study 12 more.
A group led by Allan Sandage, also of Carnegie, is using exploding stars as ``standard bombs'' for measuring distances. The idea is that these supernovae achieve an identical brightness wherever in the universe they are. By measuring the brightness, the group can determine the distance to the galaxies containing the exploded stars. Such stars can be detected 1,000 times farther away than the Cepheid stars.
The Sandage team estimates the universe's age at 11 billion to 15 billion years.
Both teams are actually measuring the rate at which the universe is expanding, a value called the ``Hubble constant.'' It is based on the theory that structures and matter in the universe - stars, galaxies and clusters of galaxies - have been all moving away from each other at a specific speed since the Big Bang, the theoretical explosion that most astronomers believe started the universe. The rate of expansion is thought to increase with the distance between objects.
LENGTH: Short : 49 linesby CNB