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
That's not to say that we can now see everything we could eventually see, if we last long enough. Some galaxies that are just beyond our current horizon will eventually be visible; we can't see them now because (as far as we can see in our reference frame) they haven't formed, yet. We can in principle watch the process of star and galaxy formation in the early universe, as the universe evolves. As the universe expands, however, the recession velocity of the earliest observable universe increases, and time dilation dictates that it evolve ever more slowly, as the velocity asymptotically approaches the speed of light. That puts a strict outer limit on the matter we'll ever be able to see.
What? You're accusing the supernaturalists of hostility?
At least there was no attempted thread hijacking this time.
I have seen less of that since the religion forum has been provided.
That makes me wonder, do the science minded go there to argue
or attempt thread hijackings?
Ah, great men do think alike... and De Gustibus Non Disputandum.....
They explain their thinking, their evidence, and how they arrive at their conclusions. Very stimulating reading. Try it.
More like imaginative thinking, as in science-FICTION.
Absolutely. That's exactly what it represents: a lower bound on the age of the Universe.
As to whether they found the faintest white Dwarf, they will get answer to that when they use the new Hubble camera, which is vastly more sensitive that the one used for this study.
The independence lies in the methodology used to obtain and analyze the data; they are based on completely different physical processes. If they were "cheating the data" their peers would point it out, and wouldn't be able to duplicate their results.
Because they stand on the shoulders of giants.
What makes you think that? The topic of the post is the conclusions the scientists are drawing with regards to the age of the universe. I certainly hope if taxpayer money is being used to fund these projects they're spending the bulk of their time on events closer to home, like our solar system. We need to be awake to whatever dangers are out there. And exploring Mars for possible colonization in the future should be high on the priority list as well.
Why does it exist?
Inflation allows for recession speeds greater than lightspeed.
You: Inflation allows for recession speeds greater than lightspeed.
Yes, but the inflationary period ended early, before the formation of galaxies began. I was asked if we could see a galaxy 100 billion light years away from us. It's light wouldn't have had time to get here.
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