LOS ANGELES, Aug. 14 (Xinhua) -- The "heavy" hydrogen that remained in our Milky Way galaxy may be much more than previously expected, U.S. astronomers reported on Monday.

The form of hydrogen called deuterium was produced a few minutes after the Big Bang, which created our universe about 14 billion years ago. But it has been slowly burned in stars and converted to heavier elements.

Scientists have believed that the "original" deuterium in the galaxy should have been 27 parts per million shortly after the Big Bang, and at least one third of it should have been destroyed for 14 billion years.

But the researchers operating NASA's Far Ultraviolet Spectroscopic Explorer satellite said that previous studies may have underestimated the deuterium levels.

The researchers found about 15 parts per million in our Milky Way and even lower -- as low as five parts per million -- elsewhere. But they also found concentrations as high as 23 parts per million in regions where supernovae or hot stars have occurred.

In fact, the current deuterium level is only about 15 percent below that "original" level. It now turns out that deuterium destruction has been occurring even more slowly than previously thought, the researchers reported in the Aug. 20 issue of the Astrophysical Journal.

"The peak galactic detection levels are likely close to the real total deuterium abundance in the Milky Way, with the rest of it in hiding, not destroyed," said George Sonneborn of NASA Goddard Space Flight Center, a co-author of the study.

If so, the new findings imply either that significantly less deuterium is being converted to helium and heavier elements in stars, or that much more deuterium has rained down onto our galaxy over its lifetime than had been previously thought, according to the researchers.

In either case, earlier models of the chemical evolution of the Milky Way galaxy will have to be revised significantly to explain the new result, they said.

Deuterium is the hydrogen isotope with one proton and one neutron in its nucleus. In the space, it produces a telltale ultraviolet spectral fingerprint that can be measured by NASA's ultraviolet satellite to determine its quantity. Enditem