How the Stars Were Born

For the first time ever, scientists are taking an incredible journey to the dawn of the universe

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A discovery like that would give Ellis bragging rights at astronomy conferences for years to come, and it would let Stark finish his dissertation with a dramatic flourish. But far more important, it would give astrophysicists their first real glimpse into a crucial and mysterious era in the evolution of the cosmos. Known as the Dark Ages of the universe, it's the 200 million-year period (more or less) after the last flash of light from the Big Bang faded and the first blush of sun-like stars began to appear. What happened during the Dark Ages set the stage for the cosmos we see today, with its billions of magnificent galaxies and everything that they contain--the shimmering gas clouds, the fiery stars, the tiny planets, the mammoth black holes.

When the Dark Ages began, the cosmos was a formless sea of particles; by the time it ended, just a couple hundred million years later, the universe was alight with young stars gathered into nascent galaxies. It was during the Dark Ages that the chemical elements we know so well--carbon, oxygen, nitrogen and most of the rest--were first forged out of primordial hydrogen and helium. And it was during this time that the great structures of the modern universe--superclusters of thousands of galaxies stretching across millions of light-years--began to assemble.

UNRAVELING A MYSTERY

So far, however, even the mightiest telescopes haven't been able to penetrate into that murky era. "We have a photo album of the universe," says Avi Loeb, a theoretical astrophysicist at Harvard University, "but it's missing pages--as though you had pictures of a child as an infant and then as a teenager, with nothing in between."

The full answer may have to wait for a new generation of telescopes expected to come on line within the next decade. In astronomy, size matters, especially for faraway objects. The bigger a telescope, the more of a distant galaxy's meager light it can gather--just as a swimming pool catches more rain than a bucket. So astronomers are looking forward to a ground-based monster with nearly 10 times the light-gathering area of the Keck, a space telescope more than 10 times as big as the Hubble and several radio telescopes with unprecedented sensitivity. Meanwhile, using the basic laws of physics, sophisticated computer simulations and tantalizing hints from existing telescopes, astronomers have put together a plausible scenario of what must have happened during the Dark Ages.

The first of those hints comes from the universe-wide flash of light that followed nearly half a million years after the Big Bang. Before that flash occurred, according to the widely accepted "standard model" of cosmology, our entire cosmos had swelled from a space smaller than an atom to something 100 billion miles across. It was then a seething maelstrom of matter so hot that subatomic particles trying to form into atoms would have been blasted apart instantly and so dense that light couldn't have traveled more than a short distance before being absorbed. If you could somehow live long enough to look around in such conditions, you would see nothing but brilliant light in all directions.

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