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Session 49 - Galactic Radioactivity, 26A1 & Solar System Origin.
Oral session, Wednesday, June 11
North Main Hall F/G,

[49.02] Direct Observation of Galactic Radioactivity

M. D. Leising (Clemson U.)

A few obscure radioactive isotopes become important tracers of Galaxy-wide nucleosynthesis by virtue of their appropriate lifetimes and gamma-ray line emission. They give us time stamps, namely today on Galactic scales, and detailed information about the physical conditions under which they were made, because they are produced only in rather specific conditions. Those that come from short-lived massive stars can give a map of star formation throughout the Galaxy. Somewhat less directly, unstable positron emitters provide similar information through the secondary annihilation photons.

Detailed measurements are relatively straightforward to interpret, but extremely difficult to make. NASA's Compton Gamma-Ray Observatory is an order of magnitude more sensitive than its predecessors, yet is just able to see the brightest Galactic features in the brightest lines. Here we outline the current techniques and results, with emphasis on distinguishing definite conclusions from ambiguous ones. We also discuss the tremendous potential of more sensitive future observations and the requirements of the instruments to achieve them.

Program listing for Wednesday