A new type of matter found inside neutron stars

Hyperaxion Jun 7, 2020

Scientists at the University of Helsinki, Finland, discovered quark-matter, a type of matter in which atomic nuclei simply do not exist.

A team of scientists at the University of Helsinki, Finland, found evidence of a new type of matter in the core of neutron stars, according to an article published in early June in the journal Nature Physics. The discovery was made possible by the combination of recent studies on theoretical physics with measurements of gravitational waves caused by the collision between two stars.

Everything around us is made up of atoms with dense nuclei, composed of protons and neutrons and surrounded by electrons with a negative charge. Within a neutron star, this atomic matter collapses and becomes an extremely dense type of nuclear matter – which is why the star is considered a huge core.

A new type of matter found inside neutron stars
(Credit: Jyrki Hokkanen, CSC – IT Center For Science).

Scientists theorized that at the core of a more massive neutron star this collapse would be so great that matter would transform into a new state, known as quark-matter, in which atomic nuclei simply would not exist. “Confirming the existence of quark cores inside neutron stars has been one of the most important goals of neutron star physics ever since this possibility was first entertained roughly 40 years ago,” said Aleksi Vuorinen, co-author of the research, in a statement.

To investigate the hypothesis, the Finnish scientists combined recent research on nuclear and particle physics with the findings from two astronomical studies – the detection of supermassive neutron stars and the measurement of gravitational waves caused by the merger of two such stars. The researchers thought that the combined analysis of this information would help them to deduce the characteristics and identity of the matter within the neutron stars.

After weeks of studying the data, the strategy worked: the team found that the particles in the core of neutron stars behave as expected from quark-matter. In addition, according to the scientists, the calculations indicate that quark-matter makes up more than half the diameter of the analyzed stars.

The researchers add that further studies on the subject are needed, as there are still many uncertainties associated with the exact structure of neutron stars. Still, they believe the new research is a big step for astronomy and physics as a whole. “There is reason to believe that the golden age of gravitational wave astrophysics is just beginning, and that we will shortly witness many more leaps like this in our understanding of nature,” noted Vuorinen.

Related topics:

Neutron star


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