Nav: Home

Merging neutron stars

February 14, 2019

The option to measure the gravitational waves of two merging neutron stars has offered the chance to answer some of the fundamental questions about the structure of matter. At the extremely high temperatures and densities in the merger scientists conjecture a phase-transition where neutrons dissolve into their constituents: quarks and gluons. In the current issue of Physical Review Letters, two international research groups report on their calculations of what the signature of such a phase transition in a gravitational wave would look like.

Quarks, the smallest building-blocks of matter, never appear alone in nature. They are always tightly bound inside the protons and neutrons. However, neutron stars, weighing as much as the Sun, but being just the size of a city like Frankfurt, possess a core so dense that a transition from neutron matter to quark matter may occur. Physicists refer to this process as a phase transition, similar to the liquid-vapor transition in water. In particular, such a phase transition is in principle possible when merging neutron stars form a very massive meta-stable object with densities exceeding that of atomic nuclei and with temperatures 10,000 times higher than in the Sun's core.

The measurement of gravitational waves emitted by merging neutron stars could serve as a messenger of possible phase transitions in outer space. The phase transition should leave a characteristic signature in the gravitational-wave signal. The research groups from Frankfurt, Darmstadt and Ohio (Goethe University/FIAS/GSI/Kent University) as well as from Darmstadt and Wroclaw (GSI/Wroclaw University) used modern supercomputers to calculate what this signature could look like. For this purpose, they used different theoretical models of the phase transition.

In case a phase transition takes place more after the actual merger, small amounts of quarks will gradually appear throughout the merged object. "With aid of the Einstein equations, we were able to show for the first time that this subtle change in the structure will produce a deviation in the gravitational-wave signal until the newly formed massive neutron star collapses under its own weight to form a black hole," explains Luciano Rezzolla, who is a professor for theoretical astrophysics at the Goethe University.

In the computer models of Dr. Andreas Bauswein from GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt a phase transition already happens directly after the merger -- a core of quark matter forms in the interior of the central object. "We succeeded to show that in this case there will be a distinct shift in the frequency of the gravitational wave signal," says Bauswein. "Thus, we identified a measurable criterion for a phase transition in gravitational waves of neutron star mergers in the future."

Not all of the details of the gravitational-wave signal are measurable with current detectors yet. However, they will become observable both with the next generation of detectors, as well as with a merger event relatively close to us. A complementary approach to answer the questions about quark matter is offered by two experiments: By colliding heavy ions at the existing HADES setup at GSI and at the future CBM detector at the Facility for Antiproton and Ion Research (FAIR), which is currently under construction at GSI, compressed nuclear matter will be produced. In the collisions, it might be possible to create temperatures and densities that are similar to those in a neutron-star merger. Both methods give new insights into the occurrence of phase transitions in nuclear matter and thus into its fundamental properties.
-end-


Helmholtz Association

Related Gravitational Waves Articles:

Are dense star clusters the origin of the gravitational waves discovered by LIGO?
Much to their surprise, scientists are finding dozens of black holes deep within densely packed collections of stars called globular clusters.
Gravitational waves detected a third time
On Jan. 4, 2017, an international team of scientists (including representatives from the University of Maryland) observed gravitational waves -- ripples in the fabric of spacetime -- for the third time.
LIGO detects gravitational waves for third time
The Laser Interferometer Gravitational-wave Observatory (LIGO) has made a third detection of gravitational waves, ripples in space and time, demonstrating that a new window in astronomy has been firmly opened.
Third gravitational wave detection offers new insight into black holes
An international team of researchers has made a third detection of gravitational waves, ripples in space and time, in a discovery that provides new insights into the mysterious nature of black holes and, potentially, dark matter.
Monash researchers uncover new gravitational wave characteristics
Monash researchers have identified a new concept -- 'orphan memory' -- which changes the current thinking around gravitational waves.
Gravitational wave kicks monster black hole out of galactic core
Astronomers have uncovered a supermassive black hole that has been propelled out of the center of a distant galaxy by what could be the awesome power of gravitational waves.
'Gravitational noise' interferes with determining the coordinates of distant sources
A group of Russian astrophysicists from the Astro Space Center (ASC) of P.N.
LIGO veteran to give talk about gravitational waves
Caltech's Stan Whitcomb, who has been involved with nearly every aspect of the development and ultimate success of the Laser Interferometer Gravitational-wave Observatory (LIGO), will give a talk about the project's historic detection of gravitational waves on Feb.
Increasing the sensitivity of next-generation gravitational wave detectors
Nearly one year ago today, the LIGO Collaboration announced the detection of gravitational waves, once again confirming Einstein's theory of General Relativity.
Gravitational biology
Akira Kudo at Tokyo Institute of Technology(Tokyo Tech) and colleagues report in Scientific Reports, December 2016, that live-imaging and transcriptome analysis of medaka fish transgenic lines lead to immediate alteration of cells responsible for bone structure formation.

Related Gravitational Waves Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Bias And Perception
How does bias distort our thinking, our listening, our beliefs... and even our search results? How can we fight it? This hour, TED speakers explore ideas about the unconscious biases that shape us. Guests include writer and broadcaster Yassmin Abdel-Magied, climatologist J. Marshall Shepherd, journalist Andreas Ekström, and experimental psychologist Tony Salvador.
Now Playing: Science for the People

#513 Dinosaur Tails
This week: dinosaurs! We're discussing dinosaur tails, bipedalism, paleontology public outreach, dinosaur MOOCs, and other neat dinosaur related things with Dr. Scott Persons from the University of Alberta, who is also the author of the book "Dinosaurs of the Alberta Badlands".