Some of universe's missing matter found

Posted by Kate Taylor

There's more atomic hydrogen in space than thought - but still not enough to solve the dark matter problem.

Atomic hydrogen is the stuff from which stars are made, by a process of coalescence which is still continuing.

And by re-examining archival data, Dr Robert Braun, chief scientist at CSIRO Astronomy and Space Science in Sydney, Australia, has made the first accurate measurement of this gas in galaxies close to our own - and discovered that they're hiding about a third more atomic hydrogen gas than previously calculated.

The study also shows that the gas is distributed very differently from how it was in the past, with much less in the galaxies' outer reachesthan billions of years ago.

"This means that it's much harder for galaxies to pull the gas in and form new stars," says Braun. "It's why stars are forming 20 times more slowly now than in the past."

However, the new finding doesn't help solve the problem of dark matter - the quantity of 'extra' matter in the universe, detectable by its gravity but not yet found.

"Even though there's more atomic hydrogen than we thought, it's not a big enough percentage to solve the dark matter problem," says Braun.

"If what we are missing had the weight of a large kangaroo, what we have found would have the weight of a small echidna."

Nevertheless, he says, the work will continue to enhance our understanding of how galaxies evolve over time.