New gravitational-wave model can bring neutron stars into even sharper focus

May 21, 2020

Gravitational-wave researchers at the University of Birmingham have developed a new model that promises to yield fresh insights into the structure and composition of neutron stars.

The model shows that vibrations, or oscillations, inside the stars can be directly measured from the gravitational-wave signal alone. This is because neutron stars will become deformed under the influence of tidal forces, causing them to oscillate at characteristic frequencies, and these 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 promising new tool to probe the elusive nature of extremely dense nuclear matter.

Neutron stars are the ultradense remnants of collapsed massive stars. They have been observed in the thousands in the electromagnetic spectrum and yet little is known about their nature. Unique information can be gleaned through measuring the gravitational waves emitted when two neutron stars meet and form a binary system. First predicted by Albert Einstein, these ripples in spacetime were first detected by the Advanced Laser Interferometer Gravitational Wave Observatory (LIGO) in 2015.

By utilising the gravitational wave signal to measure the oscillations of the neutron stars, researchers will be able to discover new insights into the interior of these stars. The study is published in Nature Communications.

Dr Geraint Pratten, of the University of Birmingham's Gravitational Wave Institute, is lead author of the study. He explained: "As the two stars spiral around each other, their shapes become distorted by the gravitational force exerted by their companion. This becomes more and more pronounced and leaves a unique imprint in the gravitational wave signal.

"The tidal forces acting on the neutron stars excite oscillations inside the star giving us insight into their internal structure. By measuring these oscillations from the gravitational-wave signal, we can extract information about the fundamental nature and composition of these mysterious objects that would otherwise be inaccessible."

The model developed by the team enables the frequency of these oscillations to be determined directly from gravitational-wave measurements for the first time. The researchers used their model on the first observed gravitational-wave signal from a binary neutron star merger - GW170817.

Co-lead author, Dr Patricia Schmidt, added: "Almost three years after the first gravitational-waves from a binary neutron star were observed, we are still finding new ways to extract more information about them from the signals. The more information we can gather by developing ever more sophisticated theoretical models, the closer we will get to revealing the true nature of neutron stars."

Next generation gravitational wave observatories planned for the 2030s, will be capable of detecting far more binary neutron stars and observing them in much greater detail than is currently possible. The model produced by the Birmingham team will make a significant contribution to this science.

"The information from this initial event was limited as there was quite a lot of background noise that made the signal difficult to isolate," says Dr Pratten. "With more sophisticated instruments we can measure the frequencies of these oscillations much more precisely and this should start to yield some really interesting insights."
-end-
Notes to editor:

The University of Birmingham is ranked amongst the world's top 100 institutions. Its work brings people from across the world to Birmingham, including researchers, teachers and more than 6,500 international students from over 150 countries.

Pratten et al (2020). 'Gravitational-Wave Asteroseismology with Fundamental Modes from Compact Binary Inspirals'. Nature Communications.

University of Birmingham

Related Gravitational Waves Articles from Brightsurf:

Weak equivalence principle violated in gravitational waves
New research published in EPJ C proves theoretically that the Weak Equivalence Principle can be violated by quantum particles in gravitational waves - the ripples in spacetime caused by colossal events such as merging black holes.

Remembrance of waves past: memory imprints motion on scattered waves
Now, it appears that between relativity and the classical (stationary) wave regime, there exists another regime of wave phenomena, where memory influences the scattering process.

New populations of black holes revealed by gravitational waves
The gravitational wave detectors LIGO and Virgo have just chalked up their biggest catch yet, a black hole 142 times the mass of the Sun, resulting from the merger of two ''lighter'' black holes.

Tabletop quantum experiment could detect gravitational waves
Tiny diamond crystals could be used as an incredibly sensitive and small gravitational detector capable of measuring gravitational waves, suggests new UCL-led research.

Gravitational waves could prove the existence of the quark-gluon plasma
According to modern particle physics, matter produced when neutron stars merge is so dense that it could exist in a state of dissolved elementary particles.

X-rays and gravitational waves will combine to illuminate massive black hole collisions
A new study by a group of researchers at the University of Birmingham has found that collisions of supermassive black holes may be simultaneously observable in both gravitational waves and X-rays at the beginning of the next decade.

Quantum expander for gravitational-wave observatories
Gravitational-wave detectors use ultra-stable laser light stored in optical cavities to achieve the high sensitivity for detecting gravitational-wave signals from merging binary black holes and neutron stars.

Gravitational lensing provides a new measurement of the expansion of the universe
Amid ongoing uncertainty around the value of the Hubble Constant, uncertainty largely created by issues around measuring distances to objects in the galaxy, scientists who used a new distance technique have derived a different Hubble value, one 'somewhat higher than the standard value,' as Tamara Davis describes it in a related Perspective.

Gravitational waves leave a detectable mark, physicists say
New research shows that gravitational waves leave behind plenty of 'memories' that could help detect them even after they've passed.

DIY gravitational waves with 'BlackHoles@Home'
Researchers hoping to better interpret data from the detection of gravitational waves generated by the collision of binary black holes are turning to the public for help.

Read More: Gravitational Waves News and Gravitational Waves Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.