Revised rates for the stellar triple-alpha process from measurement of C-12 nuclear resonances
Artikel i vetenskaplig tidskrift, 2005
In the centres of stars where the temperature is high enough, three alpha-particles (helium nuclei) are able to combine to form C-12 because of a resonant reaction leading to a nuclear excited state(1). (Stars with masses greater than similar to0.5 times that of the Sun will at some point in their lives have a central temperature high enough for this reaction to proceed.) Although the reaction rate is of critical significance for determining elemental abundances in the Universe(1), and for determining the size of the iron core of a star just before it goes supernova(2), it has hitherto been insufficiently determined(2). Here we report a measurement of the inverse process, where a C-12 nucleus decays to three alpha-particles. We find a dominant resonance at an energy of similar to11 MeV, but do not confirm the presence of a resonance at 9.1 MeV (ref. 3). We show that interference between two resonances has important effects on our measured spectrum. Using these data, we calculate the triple-a rate for temperatures from 10(7) K to 10(10) K and find significant deviations from the standard rates(3). Our rate below similar to5 x 10(7) K is higher than the previous standard, implying that the critical amounts of carbon that catalysed hydrogen burning in the first stars are produced twice as fast as previously believed(4). At temperatures above 10(9) K, our rate is much less, which modifies predicted nucleosynthesis in supernovae(5,6).
PARTICLES
B-12
BETA-DECAY
NUCLEOSYNTHESIS
ELEMENTS
ASTROPHYSICS
STARS
Författare
H. O. U. Fynbo
Aarhus Universitet
C. A. Diget
Aarhus Universitet
U. C. Bergmann
CERN
M. J. G. Borge
CSIC - Instituto de Estructura de la Materia (IEM)
J. Cederkall
CERN
P. Dendooven
Kernfysisch Versneller Institut
L. M. Fraile
CERN
S. Franchoo
CERN
V. N. Fedosseev
CERN
B. R. Fulton
University of York
W. X. Huang
Jyväskylän Yliopisto
J. Huikari
Jyväskylän Yliopisto
H. B. Jeppesen
Aarhus Universitet
A. S. Jokinen
Helsingin Yliopisto
Jyväskylän Yliopisto
P. Jones
Jyväskylän Yliopisto
Björn Jonson
Chalmers, Teknisk fysik, Subatomär fysik
U. Koster
CERN
K. Langanke
Aarhus Universitet
Mikael Meister
Chalmers
Thomas Nilsson
Chalmers, Teknisk fysik, Subatomär fysik
Göran Hugo Nyman
Chalmers, Teknisk fysik, Subatomär fysik
Y. Prezado
CSIC - Instituto de Estructura de la Materia (IEM)
K. Riisager
Aarhus Universitet
S. Rinta-Antila
Jyväskylän Yliopisto
O. Tengblad
CSIC - Instituto de Estructura de la Materia (IEM)
M. Turrion
CSIC - Instituto de Estructura de la Materia (IEM)
Y. B. Wang
Jyväskylän Yliopisto
L. Weissman
CERN
Katarina Wilhelmsen
Chalmers, Teknisk fysik, Subatomär fysik
J. Aysto
Jyväskylän Yliopisto
Helsingin Yliopisto
Nature
0028-0836 (ISSN) 1476-4687 (eISSN)
Vol. 433 7022 136-139Ämneskategorier
Subatomär fysik
DOI
10.1038/nature03219