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Radioactive 26Al from massive stars in the Galaxy
Roland Diehl1, Hubert Halloin, Karsten Kretschmer
1Max-Planck-Institut für extraterrestrische Physik, D-85748 Garching, Germany. rod@mpe.mpg.de
Nature
|January 7, 2006
Summary
Radioactive aluminum-26 (26Al) gamma-rays reveal ongoing cosmic nucleosynthesis. Measurements confirm 26Al originates galaxy-wide, supporting a supernova rate of approximately two per century.
Area of Science:
- Astrophysics
- Nuclear Astrophysics
- Cosmic Ray Physics
Background:
- Radioactive 26Al (half-life ~7.2 x 10^5 years) gamma-rays offer insights into galactic nucleosynthesis.
- Previous studies suggested both galaxy-wide and local origins for 26Al, based on gamma-ray emission and meteoritic data.
Purpose of the Study:
- To investigate the origin and distribution of 26Al in the Milky Way galaxy.
- To determine the galactic nucleosynthesis rate and core-collapse supernova frequency.
Main Methods:
- High spectral resolution measurements of 26Al gamma-ray emission at 1808.65 keV.
- Analysis of gamma-ray emission patterns to infer source region dynamics.
Main Results:
- 26Al emission regions were found to corotate with the Galaxy, supporting a galaxy-wide origin.
- The present-day equilibrium mass of 26Al was determined to be 2.8 (+/- 0.8) solar masses.
- The frequency of core-collapse supernovae was estimated at 1.9 (+/- 1.1) events per century.
Conclusions:
- Massive stars throughout the Galaxy are the dominant producers of 26Al.
- The observed 26Al distribution and dynamics support a galaxy-wide nucleosynthesis model.
- The estimated supernova rate provides crucial data for galactic chemical evolution models.
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