Great ball of hydrogen detected in cosmos

The discovery of a big ball of hydrogen in a far-flung region of the universe may help unravel one of the thorniest problems in modern cosmology: Where is the missing dark matter in the universe?

Researchers at Cardiff University in Wales have measured a giant ball of hydrogen in the Virgo cluster 50 million light years away that appears to be part of a much larger invisible galaxy of whirling debris. If the finding stands up under the scrutiny of other cosmologists, it would be the best evidence yet that most of the matter in the universe is made up not of stars but of cold dark matter hidden from earthly telescopes.

"The universe has all sorts of secrets still to reveal to us, but this shows that we are beginning to understand how to look at it in the right way. It's a really exciting discovery," said Jon Davies, a member of the Cardiff team that led the research. Other nations participating in the effort were France, Italy and Australia.

American scientists cautioned against making sweeping assumptions about the building blocks of the universe based on the European findings. "It's probably premature to say what we're seeing here," said Roger Blandford, a Stanford physicist.

"What's more significant is here we have a whole lot of gas that appears not to have formed stars," he said.

At the very least, then, the discoveries -- reported online and to be published next month in the Astrophysical Journal -- are likely to provide new insights into how and why stars form out of the cosmic foam. And, just as important, why they don't.

Based on a number of factors, including the accelerating speed at which galaxies are traveling, physicists have predicted that most of the mass of the universe is made up of unseen dark matter. While various math models have proved that dark matter must exist, the challenge has been to find clumps of it and to figure out what it is.

Researchers had been searching for a dark galaxy using radio waves, since by definition a galaxy without stars could not be seen with a visible light telescope. In 2000, the radio telescope at the University of Manchester in England detected a ball of invisible hydrogen with a mass equivalent to 100 million suns. The finding was later confirmed by the Arecibo radio telescope in Puerto Rico.

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