Neutron Star Collisions Could Reveal Secrets Of Exotic Matter

Neutron star collision. NASA/Dana Berry/Erica Drezek

Some of the most complex experiments in fundamental physics require a huge amount of energy and large laboratories. And even the most advanced laboratories, like CERN, cannot test every single idea physicists think of to explain the universe.

But beggars can’t be choosers, and two researchers from the University of Helsinki hope that an answer to quantum physics can come from the sky – in the form of neutron star collisions, to be precise.

Neutron stars are the incredibly dense remains of supernovae, and they pack masses of up to a couple of times the Sun in a diameter of 30 kilometers (19 miles). They are made of degenerate matter (where atoms are packed very tightly together), but there are doubts about what’s exactly going on at their cores.

The researchers, Aleksi Kurkela and Aleksi Vuorinen, have looked at a couple of different scenarios: Neutron stars could be made of ordinary matter in extreme conditions, or those conditions could create some state of matter we have never seen before, like deconfined (freely moving) quark matter.

In a paper, published in Physics Review Letters, the scientists have calculated how the different core scenarios would affect the gravitational waves emitted when two neutron stars merge or when one collides with a black hole. Soon, instruments like LIGO could see those events.

“Ultimately, they may answer the question, whether neutron stars are composed solely of ordinary atomic nuclei, or if they contain more exotic matter in the form of dense deconfined quark matter,” said Vuorinen in a statement.

Quarks are the fundamental components of protons and neutrons, the particles at the center of atoms. Quarks are always bound – either in a triplet (like in protons) or in a couple (like in particles called mesons), and we also have obtained tetra (four) and pentaquark (five) particles in the lab. What we haven’t found are single quarks, but this deconfined quark matter could be a state in which quarks are actually free to move in a sort of plasma.

The research provides the tools to model this quark matter to temperatures higher than absolute zero (often used as a starting point), which is necessary to model the core of neutron stars as the mergers could reach temperatures of billions of degrees.

The ball is now in LIGO’s court to hopefully find one of these objects when they re-start observations later this year.

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