Tracing massive stars in the Galaxy

The distribution of massive stars in our Galaxy, which are the likely sources of the observed gamma-rays from the isotope iron-60, is best traced by the radioactivity of aluminium-26 shown in this image from NASA's COMPTON osbervatory. Integral has made detailed observations of aluminium-26's gamma-rays. The emission from iron-60 is too faint for making images with current gamma-ray telescopes.