Bulletin of the American Physical Society
2007 APS April Meeting
Volume 52, Number 3
Saturday–Tuesday, April 14–17, 2007; Jacksonville, Florida
Session C6: Building the Elements: 50 Years of B2FH Nucleosynthesis II |
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Sponsoring Units: FHP DAP Chair: Robert V. Wagoner, Stanford University Room: Hyatt Regency Jacksonville Riverfront Grand 7 |
Saturday, April 14, 2007 1:30PM - 2:06PM |
C6.00001: Gamma rays as an indicator of nucleosynthesis Invited Speaker: In 1957 the collaboration of E. M. Burbidge, G. R. Burbidge, W. A. Fowler, and F. Hoyle, and the work by A. G. W. Cameron, laid the foundations for understanding the origin of the elements in terms of a few basic processes and astrophysical environments. Half a century after this pioneering work, there is considerable observational evidence for the basic notions of element synthesis during the big-bang, followed by hydrostatic and explosive stellar nucleosynthesis ever since the first population of stars re-illuminated the Universe, and through particle interactions in the turbulent interstellar medium. In 1969 D. D. Clayton, S. A. Colgate, and G. J. Fishman proposed to search for gamma-ray lines from the decay of 56-Ni, freshly synthesized in supernovae. Evidence for these lines was obtained for SN 1987A, and three decades after this pivotal supernova we have ample gamma-ray line evidence for ongoing nucleosynthesis in the Milky Way from surveys for individual sources and unresolved, integrated diffuse emission from an ensemble of such sources. We review the observational evidence for gamma ray lines from various species, and discuss the astrophysical implications of detections and a few puzzles suggested by lack of detections. We reflect on historic developments, assess the accomplishments, and present an outlook on the future of this branch of nuclear astrophysics. [Preview Abstract] |
Saturday, April 14, 2007 2:06PM - 2:42PM |
C6.00002: Chemical evolution of galaxies: the last frontier Invited Speaker: |
Saturday, April 14, 2007 2:42PM - 3:18PM |
C6.00003: The Samuel K. Allison Lecture: B$^{2}$FH, The CMB {\&} Cosmology Invited Speaker: Some historical aspects of the development of the theory of stellar nucleosynthesis will be discussed. I shall then go on to describe the problems originally encountered by Gamow and his associates in trying to decide where the helium was made. This leads me to a modern discussion of the origin of $^{2}$D, $^{3}$He, $^{4}$He and $^{7}$Li, originally described by B$^{2}$FH as due to the x-process. While it is generally argued, following Gamow et al, that these isotopes were synthesized in a big bang I shall show that it is equally likely that they isotopes were made in active galactic nuclei, as was the CMB, in a cyclic universe model. The key piece of observational evidence is that the amount of energy released in the conversion of hydrogen to helium in the universe is very close to the energy carried by the CMB, namely about 4.5 x 10$^{-13}$ erg cm$^{-3}$. [Preview Abstract] |
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