Hidden hydrogen could force galaxy rethink
http://physicsweb.org/articles/news/10/8/20/1
30 August 2006
An international team of researchers is claiming that deuterium -- a
heavy form of hydrogen created moments after the Big Bang -- is far
more abundant than previously estimated. Using new data from NASA's
FUSE satellite, they say that some of the deuterium has gone
unnoticed in the past because it binds as a solid to interstellar
dust grains, making it difficult to see. The claim, if true, could
force astronomers to rethink current models of how stars and galaxies
form and evolve (Astrophysical J. 647, 1106).
Deuterium -- an isotope of hydrogen containing a proton plus a
neutron -- is cosmologically significant because it is continually
destroyed in star cores by the same nuclear reactions that create
helium and other heavier elements. The amount of deuterium is
therefore far lower now than it was in the early universe. Indeed,
the shortfall in the amount of deuterium allows scientists to track
our galaxy's chemical evolution over billions of years.
But what has mystified astronomers over the years is the fact that
while primordial concentrations are about 27 parts deuterium per
million hydrogen atoms (ppm), values in the Milky Way today range
from 5-22 ppm. Three years ago, Bruce Draine from Princeton
University developed a model that could explain this anomaly. He said
that deuterium, compared to hydrogen, might preferentially bind to
interstellar dust grains, changing from an easily detectable gas to
an unobservable solid form.
See: http://physicsweb.org/articles/news/10/8/20/1
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