Jeffrey Linsky likes to solve galactic puzzles. Together with his research group, known as the "Cool Star Mafia," he recently figured out why concentrations of deuterium, a heavy form of hydrogen, vary in our galaxy. Most of the universe's deuterium was created during the Big Bang 14 billion years ago. Scientists have known for some time that the region of space near our Sun has higher concentrations of deuterium than other parts of the Milky Way. In 2004, Linsky's group explained why: supernova explosions have blasted deuterium atoms and molecules out of carbon-rich dust grains (which tightly bind them in other, less active regions of the galaxy). Once freed from the dust grains, deuterium mixes with clouds of regular hydrogen. Because our solar system has experienced several nearby supernovae in recent history, concentrations of deuterium are relatively high near us. Scientists believe that studies like Linsky's will help them develop a detailed picture of the chemical evolution of our galaxy.

Infrared light absorption by H₃⁺

Chris Greene has successfully predicted the rate of one of the most important chemical reactions that occur in interstellar clouds. He has analyzed the dissociative recombination of a simple polyatomic molecules H₃⁺ that is abundant in the hydrogen-rich interstellar environment. Greene's theoretical analysis shows that free low-energy electrons can blow apart H₃⁺ with surprising efficiency, forming either three hydrogen atoms or a hydrogen molecule (H₂) and a hydrogen atom. Recent experiments performed at Sweden's CRYRING storage ring and Germany's Test Storage Ring confirmed Greene's prediction that the rate of this chemical reaction is quite fast under interstellar conditions. This was good news because there were early, less well-controlled measurements of the recombination rate suggesting that it was at least 1000 times faster than the standard models of this process suggested. The impressive recent refinements of the original experiments, in combination with new theoretical work, have eliminated all remaining doubt. Since H₃⁺ disappears so rapidly, astrophysicists must now explain its large observed abundance in interstellar gas clouds. A likely explanation is an enhanced rate of ionization by cosmic rays. Greene's study is an example of the increasing connection between the research efforts of JILA's atomic physicists and astrophysicists.