Gamma-rays are messengers of high-energy processes throughout the universe. Nuclear reactions create radioactive isotopes, and particles which have been accelerated into the relativistic regime create non-thermal radiation. The penetrating nature of these gamma-rays implies that even sources which are invisible or optically thick in other wavelengths can be studied through their gamma-ray emission. The Compton Observatory had surveyed the gamma-ray sky and had found a few surprises beyond the images that have been obtained from cosmic-ray interactions with interstellar gas and from diffuse radioactivities originating from cosmic nucleosynthesis. ESA's INTEGRAL observatory recently made it possible to probe the low-energy gamma-ray regime at better sensitivity and, most importantly, to add spectroscopic power to resolve characteristic gamma-ray lines. We will discuss the interpretations and findings from recent observations at high energies and the corresponding source models, specifically addressing sources of nucleosynthesis and of particle acceleration in our Galaxy.

ANL Physics Division Colloquium Schedule