Steady-state nucleosynthesis throughout the Galaxy

The measurement and astrophysical interpretation of characteristic γ-ray lines from nucleosynthesis was one the prominent science goals INTEGRAL mission in particular its spectrometer SPI. Emission 26Al 60Fe decay lines, due to their My times, originates accumulated ejecta sources, appears diffuse nature. are believed originate mostly massive star clusters. radioactive observations open an interesting window trace fate flow ejecta, after they have left immediate sources birth sites, on path mix with ambient interstellar gas. emission image obtained confirms earlier findings clumpiness extent along entire plane Galaxy, supporting origin massive-star groups. spectroscopy resolved line found Doppler broadenings systematic shifts longitude, originating large-scale galactic rotation. But excess velocity 200 km s−1 suggests that decays preferentially within large superbubbles extend forward directions between spiral arms. detection nearby Orion clusters Eridanus superbubble supports this interpretation. Positrons β+ other been not explain morphology positron annihilation γ-rays at 511 keV measured by INTEGRAL. signal is but too weak for imaging interpretation, point-like/concentrated excluded. /60Fe ratio constrained a range 0.2–0.4. Beyond improving precision these results, contributions novae (through 22Na radioactivity) past neutron mergers our Galaxy (from r-process exciting new prospects remaining extensions.