Posted on 04/24/2002 6:30:34 PM PDT by longshadow
By Paul Recer
AP Science Writer
Wednesday, April 24, 2002; 4:21 PM
WASHINGTON –– The universe is about 13 billion years old, slightly younger than previously believed, according to a study that measured the cooling of the embers in ancient dying stars.
Experts said the finding gives "very comparable results" to an earlier study that used a different method to conclude that the universe burst into existence with the theoretical "Big Bang" between 13 and 14 billion years ago.
Harvey B. Richer, an astronomer at the University of British Columbia, said the Hubble Space Telescope gathered images of the faintest dying stars it could find in M4, a star cluster some 7,000 light years away.
Richer said the fading stars, called white dwarfs, are actually burnt out coals of stars that were once up to eight times the size of the sun. After they exhausted their fuel, the stars collapsed into Earth-sized spheres of cooling embers that eventually will turn cold and wink out of sight.
Earlier studies had established the rate of cooling for these stars, said Richer. By looking at the very faintest and oldest white dwarfs possible, astronomers can use this cooling rate to estimate the age of the universe.
Speaking at a news conference Wednesday, Richer said the dimmest of the white dwarfs are about 12.7 billion years old, plus or minus about half a billion years.
Richer said it is estimated that star formation did not begin until about a billion years after the Big Bang. He said this means his best estimate for age of the universe is "about 13 billion years."
Three years ago, astronomers using another method estimated the age at 13 to 14 billion years. That was based on precise measurements of the rate at which galaxies are moving apart, an expansion that started with the Big Bang. They then back-calculated – like running a movie backward – to arrive at the age estimate.
"Our results are in very good agreement" with Richer's estimate, said Wendy L. Freedman, an astronomer at the Carnegie Observatories in Pasadena, Calif., and a leader of the group performing the universe age calculations three years ago.
Bruce Margon, an astronomer at the Space Telescope Science Institute, said both conclusions are based on "a lot of assumptions" but the fact that two independent methods arrived within 10 percent of the same answer is important.
"To find an independent way to measure the age and then get essentially the same answer is a fantastic advance," said Margon. It may not be the final answer for the universe's age, he said, but is "very, very, very close."
To get the new age estimate, the Hubble Space Telescope collected light from M4 for eight days over a 67-day period. Only then did the very faintest of the white dwarfs become visible.
"These are the coolest white dwarf stars that we know about in the universe," said Richer. "These stars get cooler and cooler and less luminous as they age."
He added: "We think we have seen the faintest ones. If we haven't, then we'll have to rethink" the conclusions.
The faintest of the white dwarfs are less than one-billionth the apparent brightness of the dimmest stars visible to the naked eye.
M4 is a globular cluster, thought to be the first group of stars that formed in the Milky Way galaxy, the home galaxy for the sun, early in the history of the universe. There are about 150 globular clusters in the Milky Way; M4 was selected because it is closest to Earth.
The new age estimate for the universe is the latest in a long series of attempts to measure the passage of time since the Big Bang. Edwin Hubble, the famed astronomer who first proved that the universe is uniformly expanding, estimated in 1928 that the universe was two billion years old.
Later studies, using the very expansion that Hubble discovered, arrived at an estimate of about nine billion years for the universe age. This created a paradox for astronomers because some stars were known to be more ancient and it is impossible for stellar bodies to be older than the universe where they formed.
Freedman and others then determined, using proven values for the brightness and distance of certain stars, that the universe throughout its history has not expanded at a constant rate. Instead, the separation of galaxies is actually accelerating, pushed by a poorly understood force known as "dark energy." By adding in calculations for this mysterious force, the Freedman group arrived at the estimate of 13 to 14 billion years.
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On the Net:
Hubble Images: http://oposite.stsci.edu/pubinfo/pr/2002/10
NASA: http://www.nasa.gov
Amazing...13 billion? I could swear, it doesn't look any older than 8 billion. Really.
He added: "We think we have seen the faintest ones. If we haven't, then we'll have to rethink" the conclusions.
What if some of the white dwarfs have already "gone out"? How would you know?
the Hubble Space Telescope collected light from M4 for eight days over a 67-day period. Only then did the very faintest of the white dwarfs become visible.
If they collected light for an additional 8 days, or 80 days, would additional, "dimmer" white dwarfs become visible?
Is that the farthest cluster in which we can distinguish such stars? On the one hand, it's not all that far (cosmologically speaking); but on the other hand, resolving individual stars in such a cluster seems quite a trick.
When? Today? I didn't get it a thing. Why didn't someone tell me?
These people actually get paid to make educated guesses like this? Where can I get a job like that?
When? Today? I didn't get it a thing. Why didn't someone tell me?
Hustle down to Hallmark.
They have some of those "belated" thingys you can send.
This was addressed in the press conference today. They took exposures that were adequate to detect fainter white dwarfs if they existed, but they found none; hence they conclude that these ARE the faintest.
White dwarf stars take a gigantically long time to "go out" (which in this case means to cool until they cannot be seen).
Excellent question, grasshopper.....
It is actually the CLOSEST cluster where astronomers hoped to detect such faint beasts, because of the limitations in their equipment precluded from being able to detect objects this faint at greater distances....
..... however, the new equipment JUST installed last month on the Hubble Space Telescope will be many times more sensitive that what they used for this research, and thus will be invaluable in observing more distant clusters to see if the data collected from them supports (or contradicts) this finding.
By looking at the evidence. The universe obeys physical laws, you know.
These people actually get paid to make educated guesses like this?
No, they get paid to make measurements like this.
Where can I get a job like that?
You start by spending twelve years in college (as I did).
Well, first you start out with an IQ of say 140+, then you matriculate at a first tier university, and major in Physics, or Mathematics, or Astronomy, and after four years of hard work you get your Bachelor's degree; then you apply to grad school and get into an Astronomy/Astrophysics program, and after a couple more years of hard work, you'll have your Master's degree, and then you put in more time doing original research on your doctoral Thesis, which, with a bit of luck and a lot of hard work, might be accepted, and so you eventually get your Ph.D.
Then you go to work, continuing to do original research like these guys did, and by that time you would have come to understand how it is that scientists are able to devise observations that measure the age of the Universe using multiple independent methods, which indicate very similar results.
Actually, the error in their measurement is half a billion years, which is roughly 4%. Not bad.
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