Thermonuclear reaction rates power the models that explain how stars live, explode and create the elements. A new study co-authored by NC State faculty member Richard Longland provides a comprehensive, statistically grounded reevaluation of these rates, offering a stronger foundation for interpreting astronomical observations and simulating stellar environments.
Longland sat down with The Abstract to explain how this reevaluation can affect our future understanding of the universe.
The Abstract (TA): What are thermonuclear reaction rates and what do they tell us about the universe?
Longland: Thermonuclear reaction rates tell us how often nuclear reactions take place inside stars. These reactions release energy, which makes stars shine and, in some cases, helps drive their explosions (like in supernovae). By measuring these reaction rates in the lab, we can “peek inside” stars and understand what is happening deep in their cores – regions that telescopes can’t see directly.
TA: What were the limitations you sought to address in this new work?
Longland: Scientists have been measuring nuclear reactions for many decades, but we still don’t fully understand how precise those measurements are. In other words, we don’t clearly know the size of the uncertainties, and those uncertainties change with the temperature inside the star. This work provides a detailed overview of what we currently know and how well we know it. By mapping out the gaps and limitations, we can guide future experiments toward the most important missing information.
TA: How do you improve upon data that you can’t actually sample? We obviously can’t take samples of forming stars, so how do we determine that the data we’re using is as accurate as possible?
Longland: We study the universe like a multi-step puzzle. One piece is nuclear physics: measuring how atomic nuclei react and produce energy. Another piece is astronomy: observing the light from stars and measuring which elements are present on their surfaces. The third piece is astrophysical modeling: computer simulations that try to connect the nuclear physics to what astronomers actually observe. We constantly compare the models with observations and update the nuclear data as needed. Over many decades, this back-and-forth process has steadily improved our understanding, even though we can’t physically sample the inside of a star.
TA: What were the results in terms of improved accuracy, and how do we know they’re correct?
Longland: In this work, we brought together the complete set of published results – over 450 papers from 1954 to today – on 78 key nuclear reactions. Earlier studies had also evaluated reaction rates, but most did not carefully quantify the uncertainties: how much the rates could be off, and how confident we are in them. By including those uncertainties, we not only provide updated “best” values, but also a clear measure of how reliable they are, based on all available experimental and theoretical work.
TA: Can these rates be continually improved as we gain new data? What is the hoped for final outcome?
Longland: Yes. These rates are not final; they should be refined as new experiments and better techniques become available. Our study points out which reactions are still poorly known and where new measurements would have the biggest impact. The goal is to motivate new experimental efforts and technological advances, so that over time we can build a much more precise and complete picture of how stars produce energy and create the elements in our universe.
The work appears in the Astrophysical Journal Supplement .
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