As a tracer of continuing nucleosynthesis in our galaxy, aluminum-26, with its half-life of less than a million years, is particularly useful. The gamma rays it emits during decay cruise largely unabated through the Milky Way to detectors at Earth. An international team led by Roland Diehl (Max Planck Institute for Extraterrestrial Physics, Garching, Germany) has used 1.5 years of data from the European Space Agency’s INTEGRAL satellite to map 26 Al in the inner galaxy at high spectral resolution. The astronomers found that the radioactive tracer was redshifted on one side of the galactic center and blueshifted on the other, which demonstrates that the 26 Al occurs in star-forming regions throughout the rotating galactic plane. That finding allowed the team to estimate a total of about three solar masses of 26 Al in the entire galaxy, from which they determined current-epoch star-formation and supernova rates. Their conclusions? Our Milky...

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