Robert Braun of the Commonwealth Scientific and Industrial Research Organization has made the first accurate measurement of this gas in galaxies close to our own, the CSIRO reported Wednesday.
Following the Big Bang the universe consisted almost entirely of hydrogen atoms that over time coalesced to create galaxies and stars, a process that is still going on, scientists said.
Braun, chief scientist at the CSIRO Astronomy and Space Science in Sydney, said he's discovered galaxies around us are hiding about a third more atomic hydrogen gas than previously calculated.
However, the gas is distributed very differently from how it was in the past, he said, with much less in the galaxies' outer regions than billions of years ago.
"This means that it's much harder for galaxies to pull the gas in and form new stars," Braun said. "It's why stars are forming 20 times more slowly now than in the past."
Braun says his finding doesn't solve the problem of "Dark Matter," lots of mass in the universe detectable by its gravity but not yet identified.
"Even though there's more atomic hydrogen than we thought, it's not a big enough percentage to solve the Dark Matter problem," he said.
Braun said he analyzed observations made with radio telescopes in Australia, the United States and the Netherlands in his research.