NEW MEASUREMENTS OF DEUTERIUM at the center of our Milky Way galaxy confirm theoretical models that most deuterium, the heavy isotope of hydrogen containing one proton and one neutron, is primordial (made at the time of the big bang) and not subsequently created in galaxies or stars. A Hofstra-Williams-Colgate-Manchester (UK) team of astronomers have used the National Radio Astronomy Observatory 12-m radio telescope to scan a huge molecular cloud only 30 light years from the galactic center.

In particular they look at the spectra of hydrogen cyanide (HCN) and its deuterium counterpart DCN. In general stars are expected to be net consumers (not producers) of deuterium: they burn it into helium. But the galactic center is the Times Square of the Milky Way; it is the scene of jets, bursts, x-ray and gamma sources, a massive black hole, filaments, arcs, and other material-processing objects.

From their observed ratio of deuterium-to-hydrogen D/H, the researchers (Don Lubowich, Jay Pasachoff, Tom Balonek, and Tom Millar) deduce three things: (1) The D/H ratio is higher than you would expect in the absence of a source of virginal unprocessed material (high in D, low in heavier elements). This demonstrates that matter comparatively rich in D is indeed raining down with the cloud onto the plane of our galaxy (see figure at Physics News Graphics). In other words, the infalling matter is to the galaxy what comets are to our solar system: specimens of relatively unprocessed, primitive material. (2) For all that, the D/H ratio at the galactic center is lower than in all other places in the galaxy. This is important evidence confirming that D is not made in stars and that what D we see is made by the big bang. (3) From models of D production in quasars, the observed D/H ratio suggests that the Milky Way could not have harbored a quasar for at least a billion years and probably not for four billion years. (Lubowich et al., Nature, 29 June /pnu/2000/.)