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A greater understanding of the inner workings of neutron stars will result in a greater knowledge of the dynamics that underpin the workings of the universe and likewise could help drive future technology, said the University of Illinois Urbana-Champaign physics professor Nicolas Yunes. A brand new study led by Yunes details how recent insights into how dissipative tidal forces inside double — or binary — neutron star systems will inform our understanding of the universe.
“Neutron stars are the collapsed cores of stars and densest stable material objects within the universe, much denser and colder than conditions that particle colliders may even create,” said Yunes, who is also the founding director of the Illinois Center for Advanced Studies of the Universe. “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 within the inner workings of our universe.”
Nevertheless, a lot of these previously unseen properties became observable with the invention of gravitational waves.
“The properties of neutron stars imprint onto the gravitational waves they emit. These waves then travel thousands and thousands of light-years through space to detectors on Earth, just like the advanced European Laser Interferometer Gravitational-Wave Observatory and the Virgo Collaboration,” Yunes said. “By detecting and analyzing the waves, we will infer the properties of neutron stars and find out about their internal composition and the physics at play of their extreme environments.”
As a gravitational physicist, Yunes was concerned with determining how gravitational waves encode information in regards to the tidal forces that distort the form of neutron stars and affect their orbital motion. This information also could tell physicists more in regards to the dynamic material properties of the celebrities, reminiscent of internal friction or viscosity, “which could give us insight into out-of-equilibrium physical processes that lead to the online transfer of energy into or out of a system,” Yunes said.
Using data from the gravitational wave event identified as GW170817, Yunes, together with Illinois researchers Justin Ripley, Abhishek Hegade and Rohit Chandramouli, used computer simulations, analytical models and complicated data evaluation algorithms to confirm that out-of-equilibrium tidal forces inside binary neutron star systems are detectable via gravitational waves. The GW170817 event was not loud enough to yield a direct measurement of viscosity, but Yunes’ team was capable of place the primary observational constraints on how large viscosity might be inside neutron stars.
The study findings are published within the journal Nature Astronomy.
“That is a very important advance, particularly for ICASU and the U. of I.,” Yunes said. “Within the ’70s, ’80s and ’90s, Illinois pioneered most of the leading theories behind nuclear physics, particularly those connected to neutron stars. This legacy can proceed with access to data from the advanced LIGO and Virgo detectors, the collaborations made possible through ICASU and the many years of nuclear physics expertise already in place here.”
The University of Illinois Graduate College Dissertation Completion Fellowship and the National Science Foundation supported this study.
