map_discoveryA1_030211 Astronomers announced today a slew of remarkable findings about the early cosmos, including a firm determination of the age of the universe and the discovery of when the first stars were born.
The discoveries, based on an all-sky map that is like a baby picture of the universe, were detailed at a NASA press conference. They provide the strongest support to date for the Big Bang theory of the creation of the universe and a sub-notion within that theory that asserts that "hyperinflation" ruled during the first seconds.
The results come from measurements of radiation emitted before there were any stars.
The snapshot shows the state of the universe about 380,000 years after the Big Bang. The study of this so-called cosmic microwave background (CMB) was made using NASA's space-based Microwave Anisotropy Probe (MAP) observatory.
The data were projected to a slightly more modern yet unseen era, revealing that the universe had cooled enough for matter to condense and form the first stars just 200 million years after the Big Bang.
"That's a surprisingly early time for the turn-on of the first stars," said Charles L. Bennett, principal investigator for MAP at NASA's Goddard Space Flight Center.
The new data show the universe to be 13.7 billion years old, to within 200 million years, Bennett said. That figure has been estimated and re-estimated many times, but often with wide margins of error.
Further, the study finds that early universe was 4 percent real matter in the form of atoms, about 23 percent unseen dark matter, and about 73 percent dark energy, a totally unknown and exotic force that causes the universe to accelerate at an ever-faster pace.
Importantly, all of these figures are in line with other estimates made from data collected in the nearby universe. Bennett and others said the new results now serve as a cornerstone for modern cosmological theory and support its most widely accepted aspects.
The results also confirm that the geometry of the universe is flat. This sort of geometry, the same as what's taught in high school, does not allow two parallel lines to intersect, even across great cosmic distances.
Hyperinflation
Among the more tantalizing findings is what appears to be the first observational evidence that, as theorized, the first seconds of the universe involved extremely rapid inflation. And data shows that some of the many inflation models -- each trying to explain how this rapid expansion occurred -- can probably be ruled out, while others may work.
Andrei Linde, of Stanford University, developed some of the inflationary models that still seem to be alive. He had been greatly anticipating the results and in a telephone interview called them "extremely impressive."
Linde said inflation had seemed like science fiction when it was first introduced, about 20 years ago.
"We didn't expect in our lifetimes it would be verified," Linde said. "Now we hear the basic features of inflationary cosmology fit with observational data."
The cosmic microwave background (CMB) was unleashed about 380,000 years after the Big Bang, when the universe had first expanded enough to cool and allow atoms to form. Around that time, a dense and impenetrable primordial cloud cleared out. The radiation escaped in one form and, over time, its wavelengths were stretched to the microwave range by the perpetual expansion of the universe. The remnant radiation retains an imprint of the end of that era and hints about what occurred before, much like the patterns on a cloud's exterior provide clues to its insides.
The microwave radiation has since spread out and cooled, filling the universe. It appears to be of nearly uniform temperature across all of space, but minute variations first detected a decade ago provide the clues needed to help decipher the primordial structure of the universe.
Tiny variations
The MAP spacecraft launched June 30, 2001. These are the first findings attributed to it. MAP examines the CMB in greater detail than its predecessor, the Cosmic Background Explorer (COBE) satellite. COBE first discovered the fine variations in the CMB in 1992. It took about 3 months to get MAP into position, and since then it has been building up the data that led to today's long-anticipated announcement.
The temperature of the CMB ranges from 2.7251 to 2.7249 degrees Kelvin (a measure of degrees above absolute zero). These tiny variations reflect the earliest lumps and bumps in the universe -- seeds for galaxies and stars.
These seeds, then, formed roughly 380,000 years after the Big Bang. Scientists have no observations to tell them what happened next, but here's what they imagine:
Nodes of matter were connected by long filaments, much like a spider web. Clumps of hydrogen -- something like drops on the spider web -- developed along the filaments. Each drop had heft, gravity and a random velocity, and eventually they were drawn toward the nodes, where material gathered to generate the first galaxies.
Princeton University's David Spergel, co-investigator for MAP, said the new findings result from using the MAP data and running them against millions of computer simulations to look for matches of what the composition and geometry of the young cosmos must have been like.
"It's a lot like matching fingerprints," Spergel said. Once a match is found, then a computer model can be run forward in time to see if things turn out to match up with observations of the modern universe.
"What we find when we do that is remarkable," Spergel said. "It all fits."
Crazy universe, but true
The process is as daunting as taking a picture of a 12-hour-old baby and morphing it into an image of a 50-year-old adult, said John Bahcall of the Institute for Advanced Study in Princeton, N.J.
Bahcall was not involved in the project. But he lauded the results. "I'm astounded," he said. Bahcall said the observations and analysis were so precise that they must be believed.
"We live in an implausible, crazy universe, but one whose defining characteristics we now know," Bahcall said.
The cosmic microwave background was detected by accident in 1965, by Bell Labs researchers who heard extra noise in a radio receiver they were testing. At the time, Princeton physicist David Wilkinson had been working on a way to detect the radiation. He helped write a scientific paper back then for the Physical Review, describing the implications of the inadvertent discovery.
Wilkinson later helped develop the COBE satellite. He then worked on the MAP project. "Dave was really the father of MAP," Lyman Page, a MAP team member from Princeton, said late last year. Wilkinson died in September.
NASA announced today that the observatory had been renamed WMAP, or Wilkinson Microwave Anisotropy Probe.
The results announced today had originally been slated for a press conference last Thursday but were delayed in deference to the Space Shuttle Columbia astronauts and their families. By any account, the discoveries represent a remarkable way for NASA to get its science program heading back toward business as usual.
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How deep is the universe? Why is WMAP important? Learn this and more, as Deep Space Explorer takes you on a 3-D multimedia journey through time. Narrated by your personal tour guide, Star Trek: Deep Space 9 actress Chase Masterson. |
From speculation to science
"Before the WMAP results, astronomers and physicists had put together a very implausible picture of our universe," Bahcall said. "It had a tiny amount of ordinary matter. It had a modest amount of dark matter, whatever that is. It had an overwhelming amount of dark energy, which is a strange beast. I have to confess I was very skeptical of this picture. But the WMAP results have convinced me."
He added that every astronomer will remember when they first heard these results.
"The announcement today represents a rite of passage for cosmology from speculation to precision science," Bahcall said.
WMAP has more work to do, however, and it will continue collecting data.
Paul Steinhardt, another Princeton physicist who was not involved in WMAP project but has reviewed the findings, said the results do not rule out a so-called cyclic model of evolution, which competes with the inflationary model. The cyclic model holds that instead of a set beginning to the universe, evolution is periodic.
Both models predict virtually the same temperature fluctuations reported by WMAP, Steinhardt told SPACE.com. Inflation further predicts the generation of so-called gravitational waves, which should also be imprinted on the CMB. "That does not occur in the cyclic model," he said.
Steinhardt said the WMAP data are not yet sensitive enough to address this unresolved issue, but further observations by the satellite or other projects might yield an answer.
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