August 14, 2006
Hydrogen find alters galaxy theory
WASHINGTON -- A heavy form of hydrogen created just moments after the Big Bang has been found in larger quantities than expected in the Milky Way, a finding that could radically alter theories about star and galaxy formation, researchers said on Monday.
This form of hydrogen, called deuterium, has apparently been hiding out in interstellar dust grains, changing from an easily detectable gaseous form to a harder-to-see solid form, the French and U.S. team of astrophysicists said.Writing in the August 20 issue of the Astrophysical Journal, the researchers said they used NASA's Far Ultraviolet Spectroscopic Explorer, or FUSE, satellite, to ferret out the hidden hydrogen.
Deuterium -- a form of hydrogen with not only a proton but also a neutron in its nucleus -- produces a telltale spectral fingerprint in the ultraviolet light range, which FUSE can see.
Jeffrey Linsky of the University of Colorado, who led the study, said scientists had assumed that at least a third of the primordial deuterium present in the Milky Way was destroyed over time as it cycled through the stars.
But FUSE found deuterium exists in amounts less than 15 percent below what was there originally. And it is not distributed evenly.
"Where there are high concentrations of interstellar dust in the galaxy, we see lower concentrations of deuterium gas with FUSE," Linsky said in a statement. "And where there is less interstellar dust, we are measuring higher levels of deuterium gas."
So something in the theory is wrong, Linsky said.
"This implies that either significantly less material has been converted to helium and heavier elements in stars or that much more primordial gas has rained down onto the galaxy over its lifetime than had been thought," he said.
"In either case, our models of the chemical evolution of the Milky Way will have to be revised significantly to explain this important new result."