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| Hubble spies ancient white dwarfs in the star cluser M4, which is 7,000 light-years away in the constellation Scorpius. | |
April 24, 2002 Posted: 4:06 PM EDT (2006 GMT)
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In the past, astronomers have relied on the rate of expansion of the universe to estimate its age. Research suggests that it began with the big bang between 13 billion and 14 billion years ago.
But considering the importance of the inquiry, scientists have long sought other means to corroborate the conclusion. Now they say they think they have it.
"This new observation short-circuits getting to the age question and offers a completely independent way of pinning down that value," said Canadian astronomer Harvey Richer in a statement Wednesday.
The "clockwork stars" spotted by Hubble are extremely dim white dwarfs between 12 billion and 13 billion years old, which would make them among the first stars in the universe.
Their age would fall well within the range expected by current cosmological models, which propose that the original stars formed less than 1 billion years after the big bang.
White dwarfs are the burned-out remnants of ancient stars. Because they cool down at a predictable rate, they are much easier to date chronologically than their still burning, more erratic and youthful counterparts.
The fainter the white dwarf, the older it is.
Richer and colleagues trained Hubble on an ancient star cluster known as M4 to find some of the dimmest, and hence oldest, white dwarfs in the Milky Way.
The faded points of light are less than one-billionth the brightness of the faintest stars visible to the naked eye, according to Richer and associates, who will publish their findings in The Astrophysical Journal Letters.