Number 270 (Story #2), May 9, 1996 by Phillip F. Schewe and Ben Stein|
THE OLDEST STARS IN THE MILKY WAY ARE 15 BILLION YEARS OLD. An important adjunct to the debate over the Hubble constant is the notion that the universe cannot be younger than its oldest stars, which appear to be those in globular clusters, spherical clumps of hundreds of thousands or millions of stars found near and around our galaxy. Don VandenBerg of the University of Victoria (email@example.com, 614-721-7739) uses the Canada-France-Hawaii telescope to view the ancient, metal-poor stars (they largely lack the elements heavier than helium which many younger stars inherit from earlier supernova explosions ) in globular clusters. By plotting the stars' luminosities versus their colors, and by employing the standard model for stellar evolution, the age of the stars can be calculated. VandenBerg, speaking at last week's meeting of the American Physical Society in Indianapolis, said the oldest reliably dated stars, in globular cluster M92, were most likely 15 billion years old. Uncertainties in the determination of the distances to the clusters (affecting calculations of the stars' luminosities) might permit an age of 13 or even 12 billion years. But VandenBerg asserted that the ages could not be much younger than that. New observations of his in globular cluster M13 did not alter this assessment.