Revised rates for the stellar triple-alpha process from measurement of C-12 nuclear resonances

TY - JOUR

T1 - Revised rates for the stellar triple-alpha process from measurement of C-12 nuclear resonances

AU - Fynbo, H O U

AU - Diget, Christian Aaen

AU - Bergmann, U C

AU - Borge, M J G

AU - Cederkall, J

AU - Dendooven, P

AU - Fraile, L M

AU - Franchoo, S

AU - Fedosseev, V N

AU - Fulton, B R

AU - Huang, W X

AU - Huikari, J

AU - Jeppesen, H B

AU - Jokinen, A S

AU - Jones, P

AU - Jonson, B R

AU - Koster, U

AU - Langanke, K

AU - Meister, M

AU - Nilsson, T

AU - Nyman, G

AU - Prezado, Y

AU - Rilsager, K

AU - Rinta-Antila, S

AU - Tengblad, O

AU - Turrion, M

AU - Wang, Y B

AU - Weissman, L

AU - Wilhelmsen, K

AU - Aysto, J

AU - ISOLDE Collaboration

PY - 2005/1/13

Y1 - 2005/1/13

N2 - 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).

AB - 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).

KW - BETA-DECAY

KW - NUCLEOSYNTHESIS

KW - PARTICLES

KW - STARS

KW - ASTROPHYSICS

KW - ELEMENTS

KW - B-12

U2 - 10.1038/nature03219

DO - 10.1038/nature03219

M3 - Article

SN - 0028-0836

VL - 433

SP - 136

EP - 139

JO - Nature

JF - Nature

IS - 7022

ER -