(J. Knödlseder et al., 1999, A&A, 344, 68)
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(J. Knödlseder et al., 1999, A&A, 344, 68) |
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| The Galaxy in gamma-rays is indistinguishable from the Galaxy in microwaves! This surprising discovery is the result of a multi-wavelength study that aimed in identifying potential tracers of the 1.809 MeV gamma-ray line emission that results from the radioactive decay of 26Al. This radio-isotope has a lifetime of about one million years, hence its presence in the interstellar medium indicates recent nucleosynthesis activity. A large number of sources has been proposed as galactic factories for 26Al production, such as supernovae, massive mass-losing stars, nova explosions, or Asymptotic Giant Branch (AGB) stars. The present correlation clearly favours massive stars as producers of 26Al. In fact, 53 GHz emission arises from the ionised interstellar medium that is powered by the most massive stars in our Galaxy, that is stars that are at least 20 times more massive than the Sun! Consequently, 53 GHz emission shows a rather patchy pattern along the galactic plane that reflects the distribution of prominent star forming regions within our Galaxy. An example is the Cygnus X region which is the bright spot in the left side of the skymaps. The 1.809 MeV skymap shows exactly the same pattern. It is therefore likely that stars more massive than 20 times the Sun not only produce the galactic ionisation but also the bulk of the 26Al in the Milky Way. |
| Last update : 5-6-2002 |