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Home https://server7.kproxy.com/servlet/redirect.srv/sruj/smyrwpoii/p2/ Science https://server7.kproxy.com/servlet/redirect.srv/sruj/smyrwpoii/p2/ Merging Neutron Stars Provide Insight Into the Fundamental Properties of Matter

Merging Neutron Stars Provide Insight Into the Fundamental Properties of Matter



 Merging Neutron Stars

Simulation of merging neutron stars calculated with supercomputers. Different colors show the mass density and temperature some time after the merger has taken place and shortly before the object collapses into a black hole.

The option to measure gravitational waves of two merging neutron stars has offered a chance to answer some of the fundamental questions about matter structure . At the very high temperatures and densities in the merger scientists, the hypothesis is 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 within the protons and neutrons. However, neutron stars, weighing as much as the Sun, but being just the size of a city like Frankfurt, have a core so dense that there can be a transition from neutron matter to quark matter. 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 is a very massive meta-stable object with densities exceeding that of atomic nuclei and with temperatures 10,000 times higher than in Sun's core.

The gravitational waves measurement Emitted by merging neutron stars could serve as a messenger of possible phase transitions in the 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.

In case a phase transition takes place more after the actual merger, small amount of quarks will gradually appear across the merged object. "With the help of the Einstein equations, we were able to show for the first time that this subtle change in structure will produce a deviation in the gravitational wave signal until the newly formed massive 19459009 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 immediately after the merger – a core of quark substance forms in the interior of the central object. "We succeeded in showing 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 combinations 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 quark questions is proposed 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, the compressed nuclear matter will be produced. In the collisions, it may 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 the phase transitions in the nuclear matter and thus its fundamental properties.

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