Scientific Colloquium
March 10, 2006


"How Much Deuterium in the Milky Way?"

Deuterium, a heavy isotope of hydrogen, was created only in the Big Bang and the density of ordinary baryonic matter can be determined directly from its abundance.  The abundance of deuterium in the Milky Way Galaxy provides a lower limit to the cosmologically important primordial value and starting with the Copernicus mission in the early seventies, astronomers have tried to determine the correct value for the Milky Way.  The Far Ultraviolet Spectroscopic Explorer mission has shown that the abundance in the interstellar gas varies by a factor of 3 and that depletion on small dust grains likely causes the wide variation. The total abundance of Milky Way Deuterium is probably > 20 ppm, close to the primordial value, and it appears that only a third or less of the deuterium in the Galaxy has been consumed in stellar furnaces.  The FUSE observatory resumed operations in November after a ten month hiatus due to the loss of a reaction wheel.  I will begin with a brief status report on the satellite.



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