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Don’t touch: How scientists study the reactions inside stars

Date:
April 28, 2016
Source:
Department of Energy, Office of Science
Summary:
Nuclear scientists have devised a method that allows scientists to determine key reaction rates at stellar energies using conventional nuclear reactions.
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Left: Chart of nuclides and important astrophysical reactions. Right: SOHO-EIT image from 14 September 1997 showing a huge eruptive prominence in the resonance line of singly ionized helium (He II) at 304 Angstroms in the extreme ultraviolet. The material in the eruptive prominence is at temperatures of 60,000 - 80,000 K, much cooler than the surrounding corona, which is typically at temperatures above 1 million K.
Credit: Image courtesy of Texas A&M Cyclotron Institute and NASA

How old is the universe? What causes a star to catastrophically explode? Answering these and other questions about stellar evolutions requires knowing the rates of the reactions involved. Specifically, scientists need to understand low-energy nuclear reactions that involve stable and unstable nuclei, the positively charged core of atoms. With few exceptions, laboratory measurements are limited to stable isotopes and high energy levels and thus must be extrapolated to lower energies. Nuclear scientists at Texas A&M University devised a method, using the asymptotic normalization coefficients (ANC), that allows scientists to determine key reaction rates at stellar energies using conventional nuclear reactions.

The measurement of the ANC for the capture of a proton by a specific atom, 14N, caused nuclear scientists to reconsider the age of the universe, which had been based on earlier work. This result is just one of many important rates that have been measured by this technique.

Measurements of ANCs over the past decade have provided new information about rates of many stellar reactions that involve capturing a proton by light-mass nuclei. Such reactions are important in supernovae and other stellar burning and stellar evolution phenomena. The ANC method involves both stable and unstable nuclei. Results from the ANC research have been published in more than 70 papers in the leading peer reviewed journals. A summary of the work has been published as a review article in Reports on Progress in Physics.

Funding was provided by three organizations: Department of Energy Office of Science, grant numbers: DE-FG02-08ER41533, DE-FG02-93ER40773, DE-FG52-09NA29467, DE-SC0004958, DE-SC0004971; National Science Foundation Division of Physics, grant number: PHY-1415656; and the Italian Ministry for University Research, grant number: RBFR082838 Istituto Nazionale di Fisica Nucleare.


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Materials provided by Department of Energy, Office of Science. Note: Content may be edited for style and length.


Journal Reference:

  1. R E Tribble, C A Bertulani, M La Cognata, A M Mukhamedzhanov, C Spitaleri. Indirect techniques in nuclear astrophysics: a review. Reports on Progress in Physics, 2014; 77 (10): 106901 DOI: 10.1088/0034-4885/77/10/106901

Cite This Page:

Department of Energy, Office of Science. "Don’t touch: How scientists study the reactions inside stars." ScienceDaily. ScienceDaily, 28 April 2016. <www.sciencedaily.com/releases/2016/04/160428103520.htm>.
Department of Energy, Office of Science. (2016, April 28). Don’t touch: How scientists study the reactions inside stars. ScienceDaily. Retrieved May 23, 2017 from www.sciencedaily.com/releases/2016/04/160428103520.htm
Department of Energy, Office of Science. "Don’t touch: How scientists study the reactions inside stars." ScienceDaily. www.sciencedaily.com/releases/2016/04/160428103520.htm (accessed May 23, 2017).

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