An integral look at supernovae and stars

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 Way produces about seven new stars every year and two spectacular supernovae from massive-star collapses each century. (R. Diehl et al., Nature 439 , 45, 2006 http://dx.doi.org/10.1038/nature04364 .)