Aug 17, 2006, 18:08 GMT
Prague - Astronomers announced Thursday the discovery of two stars, one in the adolescent stage and the other nearly dead, that they say could provide a 'cosmic clock' for determining the age of the Milky Way galaxy.
The red dwarf and white dwarf stars share the Milky Way with Earth and are the faintest stars ever seen in a so-called globular star cluster, the scientists reported at a conference of the International Astronomical Union and in the latest edition of the journal Science.
'This doesn't tell us the age of the universe,' said Harvey Richer of the University of British Columbia in Vancouver, one of the report's 13 authors. 'But the age of the cluster can tell us when the stars started to shine.'
And scientists hope to determine the cluster's age by examining the dwarf stars which have each reached the end of their respective 'stellar sequences,' Richer said.
'Nature has given us a wonderful cosmic clock,' he said.
The red dwarf is at an early stage of development with barely enough mass to produce light and heat by fusing hydrogen in its core. One day it will be like our sun.
But the dying white dwarf has exhausted its fuel and is now 'burned out, like a hot rock in space,' Richer said.
Currently scientists think the NGC 6397 cluster -- with its hundreds of thousands of stars -- is about 12 billion years old. They calculate the age of the universe at 13.7 billion years.
The dim dwarfs were found by training the Hubble space telescope on the cluster, which is the second-nearest star cluster to Earth at 8,500 light years away.
It took nearly five days of focusing on the cluster with Hubble's camera to capture images of the blurry points of light.
Richer said he's been looking for ways to solve the problem of stellar age for 30 years but only Hubble made it possible by peering at objects too faint to be seen from Earth.
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