Overview
The goal of our research is to recognize the role that reactions of rare isotopes play in the cosmos. These rare isotopes are unstable nuclei that live for mere fractions of seconds, and nevertheless, in this short time of their existence, fundamentally shape the visible cosmos and the world around us. To that end, we build experimental equipment and use the unique rare isotope beams at NSCL to restage, in the laboratory, the very same nuclear processes that occur in stars or stellar explosions. The data obtained are incorporated into computer models of stellar explosions that can then be compared with astronomical observations. Often this reveals major problems in our understanding - so we identify in the model the nuclear physics that may cause the issue, and then go back to the laboratory and address it. This requires flexibility, the use of a variety of experimental techniques, and close collaboration with astronomers.
Listen to a recent NPR podcast on the origin of the elements:
Our Current Research
What is the origin of the heavy elements?
The recent observation of gravitational waves from a neutron star merger and the followup observation of the afterglow from the decay of heavy elements provides strong evidence that neutron star mergers are a major source of the heavy elements in the cosmos. We perform laboratory experiments to obtain the rates of decays and (a,n) reactions that produce the "lighter" heavy elements such as Sr, Y, Zr, Nb, Mo, Tc, Ru. With the nuclear data we can determine which elements are produced in neutron star mergers, and identify potential additional sources such as supernovae. We are also working on simulations that more clearly identify the nuclear physics needed to interpret neutron star merger observations. Watch JINA-CEE Live Stream Discussion Watch Hendrik's TED-X Talk |
NSF/LIGO/Sonoma State University/A. Simonnet
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What do X-ray bursts tell us about neutron stars?
X-ray bursts are the most frequent thermonuclear explosions in our Galaxy with several bursts occurring every hour. They are explosions on the surface of neutron stars that accrete stellar material from a companion star. The minute long light curve is shaped by nuclear reactions on rare isotopes and also contains information about the neutron star and the stellar system. To enable interpretation of the bursts we measure these reaction rates in the laboratory and work on models that quantify the influence of each of the 100s of different reactions that occur. Read our Review Article |
What do cooling neutron stars tell us about ultra-dense matter?
A neutron star contains the entire mass of the Sun in a sphere the size of a small city. This is one of the densest environments in the universe and strange things happen inside these stars that cannot be studied anywhere else. Recent X-ray observations showed that some neutron stars have relatively rapidly cooling outer layers, and the time evolution of the temperature over a few years can reveal information about the matter inside - for example the existence of super-fluid material or nuclear pasta. We measure the nuclear reactions that heat and cool the crust during the previous mass accretion phase to enable such an analysis. We also run computer simulations of the 100s of reactions that operate in the crust to identify which ones matter the most. |
NASA/Chandra/Wijnands et al.
Chandra X-ray observations of neutron star KS1731-260 initially (left) and after 12 years of cooling (right) |
More About Nuclear Astrophysics
Read the new "Horizons: nuclear astrophysics in the 2020s and beyond" white paper that outlines a community vision for the field of nuclear astrophysics that cuts across nuclear physics and astrophysics international communities. Article.
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