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
It's only my opinion that the universe goes on much farther than we know, so predicting its age is not possible. If there are galaxies 100 trillion light years away we can't see, then that means the universe is at least 100 trillion years old.
Well, what do we see? When we look at distant galaxies we see something called spectral redshifts -- doppler shifts in the spectral emissions of well known elements. Everywhere we look these objects seem to be moving away from us. How odd. The closer ones are moving away slower, and the farther ones are moving away faster.
If you project those motions backward, it is inescapable that we came from a central point -- a "big bang."
Well, how long ago? We know the rate of speed because the doppler shift obeys specific physical laws. We didn't initially know the distances.
One of the earliest methods was to use the brightness of a certain class of variable stars, called Cephids. They could use paralax, triangulation, on close Cephids and get a correlation between their rate of variation, their brightness, and hence their distance. This seemed a good plan because the Cephids were remarkably uniform in that regard. They were a good measuring stick.
So that was one of the early estimates of the size of the universe. But eventually a second class of Cephids were discovered and all the brightness/rate variaition/ distance calculations had to be recomputed.
Those are the two early methods I can recall off the top of my head.
So we haven't seen anything further out than these most distant objects, and they all have that receding redshift indicative of being sourced from the central big bang. So that puts an upper limit on the age of the universe and the Cephid (and now other means) puts a limit on the distance.
There is no evidence that the universe is infinite nor more than 14 billion years old. I won't speculate beyond the limits of evidence.
Good question. My next door neighbor said something long time ago that stuck with me - "how big is big"? In other words, what seems enormous to us may be nothing compared to something else. What he meant was it's possible we're just beings inside some other life form, and if that's the case the universe would not be infinite.
Did you happen to see the threads on gravistars the past couple of days? If not, I might be able to link to them.
Oh, but the age disparity is precisely what makes this methodology so useful. Globular clusters have the OLDEST stars in the galaxy. They look at the oldest stars in the galaxy, and then looked for the faintest white dwarfs among them (meaning the oldest of the oldest, so to speak).
Thus, the age of the oldest visible white dwarf defines a lower bound for the age of the Universe. To this age (12.7 x 109) they add a billion years, which is the minimum estimate of the length of time it takes for stars to form AFTER the Universe started. Thus the minimum age for the Universe is 13.7 billion years (+/- 0.5 billion) by this method.
It would. But I am afraid it might not be. That would turn things inside out.
That's like a deja vu with Professor Donald Sutherland in the potsmoking party in Animal House!
First, you go to college. The catch is that you have to spend most of your time there acutally studying, as opposed to protesting and harassing women like certain ex-POTUSes who shall remain nameless.
Exactly.
I don't recall stating that it was "incontrovertible" anywhere.
But what is clearly true is that the confidence in the age of the Universe becomes MUCH greater if it is supported by multiple independent methodologies.
You do agree, don't you?
The big bang theory and the expanding universe may be strong possibilities given the research and what we know. But does current technology prevent us from seeing out farther than we do now? Could it even be possible to discover galaxies 100 billion or more light years away? This is why I'm skeptical of any claims to age, because there's so much out there we don't know yet.
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