The physics of massive nuclei can be studied by measuring the ‘note’ on which tire resonance between fusing neutron stars causes the solid crust of the neutron stars to shatter. Credit: University of Bath
Space scientists have found a new way to study the internal structure of neutron stars, which provides clues about the composition of matter at the atomic level.
Space scientists at the University of Bath in the United Kingdom have found a new way to study the internal structure of neutron stars, giving nuclear physicists a new tool to study the structures that make up matter at the atomic level.
Neutron stars are dead stars that are compressed by gravity to the size of small cities. It contains the most extreme matter in the universe, which means that it is the densest objects that exist (as the earth to the density of a neutron star, it would measure a few hundred meters in diameter, and all people would fit in a teaspoon). This makes neutron stars unique natural laboratories for nuclear physicists, whose understanding of the power that binds sub-atomic particles is limited to their work on earth-bound atomic nuclei. Studying how this power behaves under extreme conditions provides a way to deepen their knowledge.
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In a study described in the Monthly notices from the Royal Astronomical Society, Bath astrophysicists have found that the action of two neutron stars moving ever faster as they rotate in the direction of a violent collision gives an indication of the composition of neutron star material. From this information, nuclear physicists will be in a stronger position to calculate the forces that determine the structure of all matter.
Resonance
It is through the phenomenon of resonance that the Bath team made its discovery. Resonance occurs when force is applied to an object at its natural frequency, which generates a large, often catastrophic, vibrational motion. A well-known example of resonance is found when an opera singer breaks a glass by singing loud enough at a frequency corresponding to the oscillation modes of the glass.
When some in-spiral neutron stars reach a resonance, their solid crust – which is thought to be 10 billion times stronger than steel – breaks. This results in the release of a bright burst of gamma rays (called ‘Resonant Shattering Flare’) that can be seen by satellites. The in-spiraling stars also release gravity waves which can be detected by instruments on earth. The Bath researchers found that they could calculate the ‘symmetry energy’ of the neutron star by measuring both the torch and the gravitational wave signal.
Symmetry energy is one of the properties of nuclear material. It controls the ratio of the sub-atomic particles (protons and neutrons) that make up a nucleus, and how this ratio changes when subjected to the extreme densities found in neutron stars. A reading for symmetry energy will therefore give a strong indication of the composition of neutron stars, and upon expansion, the processes by which all protons and neutrons couple, and the forces that determine the structure of all matter.
The researchers emphasize that studying measurements obtained by studying the resonance of neutron stars using a combination of gamma rays and gravitational waves would be complementary to, rather than a substitute for, the laboratory experiments of nuclear physicists.
“By studying neutron stars and the cataclysmic final motions of these massive objects, we can understand something about the tiny, tiny nuclei that make up an extremely dense matter,” said Dr. David Tsang, Bath astrophysicist. huge difference in scale makes it fascinating. “
The PhD student in astrophysics, Duncan Neill, who led the research, added: ‘I like that this work looks at the same thing being studied by nuclear physicists. They look at small particles and our astrophysicists look at objects and events from many millions of light years. We look at the same thing in a very different way. ‘
Dr. Will Newton, astrophysicist at Texas A&M University-Commerce and project contributor, said: “Although the force that binds quarks in neutrons and protons is not well understood, it works well when large numbers of neutrons and protons come together. The attempt to improve this understanding is aided by experimental nuclear physics data, but all the nuclei we examine on earth have a similar number of neutrons and protons that have approximately the same density.
“In neutron stars, nature offers us a very different environment to explore nuclear physics: matter that consists mostly of neutrons and extends over a wide range of densities, up to ten times the density of atomic nuclei. In this paper we show how we can measure a certain property of this matter – the energy of symmetry – from distances of hundreds of millions of light-years away. It can shed light on the fundamental workings of nuclei. ”
Reference: “Resonant Shattering Flares as Multimessenger Probes of the Nuclear Symmetry Energy” by Duncan Neill, William G Newton and David Tsang, March 26, 2021, Monthly notices from the Royal Astronomical Society.
DOI: 10.1093 / mnras / stab764