Stellar Reaction Recreated in the Lab

In space, some stars are known to feed off one another. As they suck energy from their neighbors, these stars trade chemical elements. By understanding the dynamics of these stellar reactions, we can learn more about the cosmic recipes in everything from planets and particles in space to people and life on Earth.

Scientists at the Department of Energy’s (DOE) Oak Ridge National Laboratory (ORNL) and Michigan State University (MSU) have reproduced in a laboratory one of the specific reactions that occurs when a neutron star gobbles up mass from a nearby companion star. Neutron stars are super dense stars with a center that has an almighty gravitational pull. The force is so powerful that it can siphon off enough hydrogen and helium from a nearby star to create an explosion on the neutron star’s surface. These explosions, fueled by the nuclear reactions, can create new versions of chemical elements.

This effort has collaborators from nine institutions across three countries, including the Facility for Rare Isotope Beams, a DOE Office of Science user facility that MSU operates. In their lab environment, the team of researchers used the world’s highest-density helium jet to recreate the nuclear reaction. The experiment produced the same physics on Earth that occurs in outer space. A beam of an unstable version of a chemical element seen in space (argon-34) struck a target filled with a version of helium (known as helium-4 nuclei). High-resolution detectors surrounding the gas jet measured the energies and angles of the particles from the explosion. Accounting for the conservation of energy and momentum, the scientists worked backwards to understand the dynamics of the reaction.

The results revealed to the team how many of those nuclear reactions occurred in the process. They also provided the specific energy state of the newly created potassium element. Both data points aligned with existing theoretical models. As a next step, the researchers plan to address whether the statistical model could be valid for other reactions taking place in stars rather than earthly laboratories.

“Our result has shown that the statistical model is valid for this particular reaction, and that removes a tremendous uncertainty from our understanding of neutron stars,” said Kelly Chipps, who is leading the effort at ORNL. “It means that we now have a better grasp of how those nuclear reactions are proceeding.”

DOE’s Office of Science, the National Science Foundation, and ORNL’s Laboratory Directed Research and Development program supported the work.

Author: Ashleigh Papp (ashleighpapp@science.doe.gov) is a science writer and multimedia producer in the Office of Science.

Explore more on these topics:

• National Labs
• Nuclear
• Particle/High Energy Physics
• Space Exploration and the Universe

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