A new National Science Foundation (NSF)–supported Physics Frontier Center in which Penn State is a partner — the Network for Neutrinos, Nuclear Astrophysics, and Symmetries (N3AS) — expands the reach and depth of existing capabilities in modeling one of the most violent events in the universe: the merger of neutron stars and its explosive aftermath.
Awarded $10.9 million over five years by NSF, the UC Berkeley–based center will focus on using the most extreme environments found in astrophysics — the Big Bang, supernovae, and neutron star and black hole mergers — as laboratories for testing fundamental physics under conditions beyond the reach of Earth-based labs.
“As part of the Physics Frontier Center’s activities, our numerical relativity group at Penn State will perform supercomputer simulations of neutron star mergers and supernovae that will bridge the dense matter and neutrino physics developed by others nodes in the center to the astronomical observations of these events,” said David Radice, assistant professor of physics and of astronomy and astrophysics in the University’s Eberly College of Science.
The center will focus on a number of research areas, including:
- The description of the ultradense, neutron-rich nuclear matter found at the centers of supernovae and neutron stars.
- Neutrinos, responsible for most of the energy and particle count in astrophysical explosions.
- Nucleosynthesis, the creation of new elements — particularly elements heavier than iron that are not produced in the Big Bang or by the stars as they burn.
- Dark matter, which makes up about 85 percent of the mass of the universe but has only been observed indirectly through its gravitational effects; dark matter can influence how supernovae and neutron stars cool.
- The use of high-performance computing to simulate mergers and supernovae.
With a growing network of ultrasensitive gravitational wave detectors — including a new underground detector in Japan, called KAGRA (Kamioka Gravitational-Wave Detector), which will be teamed with existing detectors LIGO (Laser Interferometer Gravitational-Wave Observatory) in the U.S. and Virgo (Europe’s observatory) in Italy — the center will be able to pinpoint new cataclysmic events in the cosmos, including neutron star mergers.
Gravitational waves produced in a merger of two neutron stars provide rich information on the structure of these exotic objects, in which a mass roughly comparable to that of the sun is squeezed into a sphere with a radius of about six miles. How neutron stars deform during the merger reflects properties of nuclear matter at several times the density of an atom’s nucleus.
The center will feature close ties with RIKEN, Japan’s largest research institution, and CNRS, the French National Center for Scientific Research. It will support a fellowship program that hires four fellows per year to conduct research for three years; the first two years are spent at an N3AS institution of the fellow’s choosing, and the fellow must move to a different institution for the third year of research.
Institutional members of the center include UC Berkeley, Los Alamos National Laboratory, North Carolina State University, Northwestern University, Ohio University, Penn State, UC San Diego, University of Kentucky, University of Minnesota, University of New Hampshire, University of Notre Dame, University of Washington, and University of Wisconsin, Madison.