August 3, 2021
The University of Tennessee, Knoxville, is partnering with institutions across the country in a multi-million dollar project to study the merger of neutron stars—objects with mass 1.5 to 2.5 times that of our sun that serve as a model for atoms and generate elements heavier than iron.
The National Science Foundation is investing $3.25 million to create the Nuclear Physics of Multi-Messenger Mergers research hub, which capitalizes on Nobel Prize-winning science and advanced computational tools to learn about the nature of matter in ways not possible in a standard laboratory. The hub will emphasize training a diverse cadre of new doctoral graduates to ensure a next generation of scientists will broaden the field and carry the research forward.
When the core of a massive star collapses under the weight of its own gravity, the result may be a black hole or a much denser neutron star. The 2015 detection of gravitational waves—"ripples" in space-time set off by black hole collisions—not only won a Nobel Prize but also gave astrophysicists an additional tool to observe objects in the universe. In 2017 scientists detected a gravitational wave signal from the collision of two neutron stars.
For millennia the best information neutron stars provided to curious astronomers came from photons—quanta of light. Having additional data from gravitational waves ushers in a new era of "multi-messenger" astronomy. Coupled with advanced computational power, this approach can help scientists create ever-more sophisticated simulations to link their neutron star observations to nuclear physics and help them answer fundamental questions about matter.
Andrew Steiner, associate professor of physics, is the principal investigator on the project.
"One way I like to think of it is using neutron stars as a laboratory," he said. "Everything is made out of atoms and nuclei, and nuclei are dictated by how neutrons and protons interact. One way of understanding how they work is by pushing them a little in one direction or the other. We make them a little hotter, a little denser; we put them in a different environment (or) give them a little bit of a magnetic field—all of these things are kind of knobs that we turn so that we can figure out more about what’s going on. Neutron stars allow us to study matter in many different ways."
He explained that the detection of gravitational waves was a strong indicator that neutron star mergers play an important role in creating heavy nuclei, such as the iodine necessary for our thyroids to function.
"We all carry a little neutron star within us," Steiner said.
The rapid development of tools and expertise has created a timely opportunity to form this hub, which includes partners at the University of Houston, Indiana University, Pennsylvania State University, and Syracuse University. The collaboration includes another 13 senior investigators (including UT Physics Professor Raph Hix) representing universities and national laboratories across the United States, as well as collaborators from across the world.
"It allows us to really create a community of scientists working together on this because this is just too big for us to do by ourselves," Steiner said.
A key element of the project is supporting postdoctoral associates to bring early-career scientists into the field, especially from under-represented groups.
"We have many more questions than we could ever answer with the actual person power we have," he said. "This is really about training the next generation."
More information is at the collaboration’s website.