Astronomers are closing in on two of the most elusive statistics ever _ the age and size of the universe.
The Hubble Space Telescope has yielded observations that show it can establish a cosmic yardstick and determine how fast the universe is expanding, scientists say.
The results also renew a long-standing paradox in which the universe appears to be younger than some of its stars. That impossibility suggests scientists will have to revise theories of the cosmos.
One goal of the Hubble telescope is to make observations that would let scientists accurately measure the distances to faraway objects. The cosmic map now is like a roadmap without a distance scale; scientists know how various distances compare but don't know just what those distances are.
With an accurate distance scale, scientists could determine how fast the universe is expanding. And that rate could be combined with some scientific assumptions to estimate the age of the universe.
A team of scientists trained the Hubble telescope on a distant galaxy called M100.
In today's issue of the journal, Nature, researchers report that the observations let them estimate with good precision that the M100 galaxy is some 56-million light-years away. A light-year is the distance light travels in one year, about 5.9-trillion miles.
The finding let the scientists make a rough estimate of the rate of expansion of the universe, a long-debated number called the Hubble constant. More observations are needed to reach a more precise estimate, they said.
The new estimate of the expansion rate implies that the universe is a relatively young 8-billion years old. The age becomes 12-billion years old if one assumes the universe contains far less matter than many theorists believe. Some prior age estimates have ranged up to 16-billion years, said Barry Madore, an astronomy professor at the California Institute of Technology and a member of the research team.