(ORDO NEWS) — Gravitational wave researchers from the University of Birmingham have developed a new model that promises to give a new idea of the structure and composition of neutron stars.
The model shows that the star’s internal vibrations can be measured directly from a single gravitational wave signal. This is because neutron stars are deformed under the influence of tidal forces, causing them to oscillate with characteristic frequencies at which they encode unique information about the star in the gravitational wave signal.
This makes asteroseismology – the study of stellar oscillations – with gravitational waves from colliding neutron stars a new promising tool for exploring the elusive nature of extremely dense nuclear matter.
Neutron stars are superdense remnants of collapsed massive stars. They were observed by thousands in the electromagnetic spectrum, and yet little is known about their nature. Unique information can be obtained by measuring gravitational waves emitted at the moment when two neutron stars meet and form a binary system. First predicted by Albert Einstein, these pulsations in space-time were first detected by an advanced laser interferometer of the gravitational-wave observatory (LIGO) in 2015.
Using the gravitational wave signal to measure the vibrations of neutron stars, researchers will be able to discover a new understanding of the internal composition of these stars. The study is published in Nature Communications.
Dr. Gerain Pratten of the Institute of Gravitational Waves of the University of Birmingham is the lead author of the study. He explained: “As two stars rotate around each other, their shapes are distorted by the gravitational force created by their satellite. This is becoming more pronounced and leaves a unique imprint in the signal of the gravitational wave. ”
“Tidal forces acting on neutron stars excite vibrations inside the star, giving us an idea of their internal structure. By measuring these fluctuations from the gravitational wave signal, we can extract information about the fundamental nature and composition of these mysterious objects, which otherwise might be inaccessible. ”
The model developed by the group allows for the first time to determine the frequency of these oscillations directly from measurements of gravitational waves. The researchers used their model on the first observed signal of a gravitational wave from the fusion of a double neutron star – GW170817.
Co-author Dr. Patricia Schmidt added: “Almost three years after the first gravitational waves from a binary neutron star were observed, we still find new ways to extract additional information from the signals received from them. “The more information we can collect by developing more and more complex theoretical models, the closer we will be to discover the true nature of neutron stars.”
The next-generation observatories of gravitational waves, the opening of which is planned for the 2030s, will be able to detect much more binary neutron stars and observe them in much more detail than is possible at present. A model created by a team from Birmingham will make a significant contribution to this science.
“Information about this event was limited because there was quite a bit of background noise that made signal isolation difficult,” says Dr. Pratten. “With more sophisticated instruments, we can measure the frequencies of these vibrations much more accurately, and this will give us really interesting ideas.”
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