You may now preview the components for Hubble release #STScI-PR02-10 A group of researchers using the Hubble Space Telescope today claimed a more accurate measurement of the beginning of time, an extremely important but highly debated cosmic birth date.
The universe is between 13 billion and 14 billion years old, according to the new study.
It's no secret that astronomers don't know how long the universe has been around. For decades they have estimated the age, based on where galaxies are and how fast they move. Because galaxies are all moving away from each other, a discovery made by Edwin Hubble in the late 1920s, leading theorists have long figured things all originated in one point in space, billions of years ago, in a Big Bang.
But age estimates based on this expanding universe typically range from 12 billion to 15 billion years, with each new study working from a slightly different set of numbers as more data is gathered on the rate of expansion.
Other theories of the universe's birth and evolution are dependent on knowing when it all began.
Clockwork stars
The new study claims an independent reading of the universe's age based on the discovery of dim, ancient, burned-out stars in our own galaxy that the astronomers said serve as "clockwork stars."
"This new observation short-circuits getting to the age question, and offers a completely independent way of pinning down that value," said study team member Harvey Richer of the University of British Columbia.
The study found that these white dwarf stars, essentially shriveled stellar corpses, are 12 billion to 13 billion years old. Earlier Hubble data had shown that the first stars in the universe formed less than 1 billion years after the Big Bang, a number that was added to the age of the white dwarfs to calculate the newest estimate for the age of the universe.
Before the stars
Prior to the first stars being born, the universe was a relatively smooth distribution of matter and energy, scientists think. But lumps and threads of material formed
sometime in that first billion years or so, and then gravity went to work collecting matter into larger clumps and filaments.Eventually, the clumps grew large enough to collapse and form the first stars and galaxies. Over the eons, the stars used all their original fuel. Some exploded. Others cast off their outer layers and then shrunk. Many of them cling to existence today as mere remnants of their former selves -- the white dwarfs.
Richer and his colleagues said their dating technique was similar to determining how long ago a campfire was burning by measuring the temperature of the smoldering coals. White dwarf stars still emit heat, but like a dying fire's embers they are not as hot as full-blown stars.
Previous research has determined the rate at which white dwarfs cool with age, making them useful as clocks.
The white dwarfs in the new study were found in a so-called globular cluster called M4. This and other ancient star clusters are thought to have formed the original Milky Way Galaxy, well before the current pinwheel design took shape.
The results, presented today at a NASA press conference, will be published in the Astrophysical Journal Letters.
History of findings
The Hubble study builds on expectations that go back to at least 1999, when researchers at the European Southern Observatory confirmed the existence of white dwarfs in a cluster of stars called NGC 6397. At that time, astronomers said white dwarfs might be common, though hidden in similar globular clusters throughout the Milky Way.
And,
they said then, these white dwarfs might be used to calculate the age of the universe.White dwarf stars are typically about the size of Earth, yet they can contain as much mass as the Sun. A teaspoonful of a white dwarf is therefore said to weigh as much as an elephant.
Because they are hard to spot, white dwarfs are thought to make up a small percentage of the missing mass, or dark matter, in the universe. In fact, one recent study suggested that there may be
more white dwarfs in our galaxy than all the regular bright stars combined.The globular cluster M4 is about 7,000 light-years away -- the closest known along with NGC 6397.
The white dwarfs found in M4 are less than one-billionth as bright as the faintest stars you can see with your eyes on a dark night in the desert. Detecting them with the orbiting observatory required collecting photons of light for almost eight days, in multiple exposures that spanned a 67-day period.
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