Reviewed by Lexie CornerSep 6 2024
In a recent study published in the journal Nature Astronomy, researchers at the University of Illinois Urbana-Champaign offered new insights into how dissipative tidal forces in binary neutron star systems could advance our understanding of the universe.
Illinois researchers Rohit Chandramouli, left, Professor Nicolas Yunes, and Abhishek Hegade used computer simulations, analytical models, and sophisticated data analyses to verify that forces within binary neutron star systems are detectable via gravitational waves. Image Credit: Fred Zwicky
According to Nicolas Yunes, a physics professor at the University of Illinois Urbana-Champaign, a deeper understanding of the inner workings of neutron stars could not only enhance knowledge of the universe's dynamics but also contribute to the development of future technologies. Yunes led the research team.
Neutron stars are the collapsed cores of stars and densest stable material objects in the universe, much denser and colder than conditions that particle colliders can even create.
Nicolas Yunes, Founding Director and Professor, Illinois Center for Advanced Studies of the Universe, University of Illinois Urbana-Champaign
Yunes added, “The mere existence of neutron stars tells us that there are unseen properties related to astrophysics, gravitational physics, and nuclear physics that play a critical role in the inner workings of our universe.”
However, the discovery of gravitational waves has made many of these previously unknown properties observable.
The properties of neutron stars imprint onto the gravitational waves they emit. These waves then travel millions of light-years through space to detectors on Earth, like the advanced European Laser Interferometer Gravitational-Wave Observatory and the Virgo Collaboration.
Nicolas Yunes, Founding Director and Professor, Illinois Center for Advanced Studies of the Universe, University of Illinois Urbana-Champaign
Yunes said, “By detecting and analyzing the waves, we can infer the properties of neutron stars and learn about their internal composition and the physics at play in their extreme environments.”
Yunes, a gravitational physicist, sought to understand how information about tidal forces—those that alter the shape of neutron stars and affect their orbital motion—is encoded in gravitational waves. Additionally, this data could provide physicists with insights into the stars' dynamic material properties, such as internal friction and viscosity.
“Which might give us insight into out-of-equilibrium physical processes that result in the net transfer of energy into or out of a system,” said Yunes.
Along with Illinois researchers Justin Ripley, Abhishek Hegade, and Rohit Chandramouli, Yunes utilized data from the gravitational wave event GW170817 to confirm that out-of-equilibrium tidal forces in binary neutron star systems are detectable through gravitational waves. This was achieved using computer simulations, analytical models, and advanced data analysis algorithms. While Yunes' team was unable to directly measure viscosity from the GW170817 event, they succeeded in placing the first observational limits on the maximum viscosity that can exist inside neutron stars.
This is an important advance, particularly for ICASU and the U. of I. In the '70s, '80s, and '90s, Illinois pioneered many of the leading theories behind nuclear physics, particularly those connected to neutron stars. This legacy can continue with access to data from the advanced LIGO and Virgo detectors; the collaborations made possible through ICASU, and the decades of nuclear physics expertise already in place here.
Nicolas Yunes, Founding Director and Professor, Illinois Center for Advanced Studies of the Universe, University of Illinois Urbana-Champaign
The National Science Foundation and the University of Illinois Graduate College Dissertation Completion Fellowship funded this research.