Merging Neutron Stars Shed Light on Fundamental Matter

Leading researchers have shared their calculations of what the phase signature of two merging neutron stars in a gravitational wave would look like. Measuring the gravitational waves of two merging neutron stars offers the opportunity to answer underlying questions about the structure of matter. 

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Scientists believe that such a merger would create extremely high temperatures and densities that a phase-transition where neutrons dissolve into their constituents: quarks and gluons is likely. The calculations based on such an event have been outlined by research groups from The research groups from Frankfurt, Darmstadt, and Ohio (Goethe University/FIAS/GSI/Kent University) as well as from Darmstadt and Wroclaw (GSI/Wroclaw University) and published in the recent edition of Physical Review Letters. 

Quarks go solo

Quarks are never observed alone in nature. The fundamental building blocks of matter are always tightly bound inside the protons and neutrons. However neutron stars with mass as much as the sun but a physical size as small as a city like Frankfurt have a core so dense that a transition from neutron matter to quark matter may occur. 

Known by the physicists as a phase transition, the event is principally possible when merging neutron stars come together and form object with densities exceeding that of atomic nuclei and with a temperature 10,000 times higher than in the Sun's core. 

Deviation in waves signal spells bigger things

The researchers propose that the measurement of gravitational waves emitted by merging neutron stars could serve as a messenger of possible phase transitions in outer space. The research groups used supercomputers to calculate what this signature could look like. 

"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. 

Physicists wait for better tech

Dr. Andreas Bauswein from GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt found that in their computer models a phase transition already happens directly after the merger -a core of quark matter forms in the interior of the central object.

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"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 gravitational-wave signals are measurable with current technology. 

However, it is expected they will become observable as technology improves. Additional experiments have been designed to answer other questions about quark matter. One of these involves 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).