In the heart of neutron stars, at a temperature of more than a trillion degrees, scientists have discovered strange forms of fundamental particles that resemble “pasta”. These unique nuclear forms have been found to penetrate deeper into the nuclei of neutron stars than previously believed, potentially leading to significant changes in the properties of these celestial bodies.
Neutron stars are the remnants of the most massive stars in the universe. Despite their relatively small size, they contain material equivalent to several suns, due to extreme compression. Under such conditions, atomic and nuclear bonds are destroyed, resulting in the unusual composition of these dead stars.
The exact structure of neutron stars remains a mystery to astronomers. It is believed that their outer layers consist mainly of neutrons, but within their nuclei, the pressure and density are so immense that even neutrons themselves are destroyed, leaving behind a dense semi-liquid composed of quarks.
The interplay between the quark nucleus and the neutron outer layer determines the characteristics of neutron stars, including their rotation, vibrational behavior, and their response to collisions with other neutron stars.
Two physicists sought to investigate this phenomenon, focusing on the complex transition zone between the quark nucleus and the neutron outer layers. Within this zone, they discovered “nuclear pasta” – compact clusters of neutrons immersed in a sea of quarks. These structures take on various shapes, resembling different types of pasta such as blobs, tubes, rods, and bubbles.
The researchers identified the crucial role of curvature tension, which is the resistance of a curved shape to being straightened. This tension is similar to the surface tension of liquids, where the liquid resists external forces attempting to penetrate its surface.
By considering curvature stresses, the researchers found that certain forms of nuclear pasta, such as tubes and bubbles, can exist at higher densities than previously thought possible, while other forms like drops and rods do not persist for long periods.
Although these changes may seem minor, they could have significant consequences. When neutron stars collide and result in kilonovae explosions, the specific details of these explosions, especially their ability to generate heavier elements in the periodic table, depend on the internal structure of neutron stars. The extent to which neutrons reach the core and the forms they assume can alter the outcome of these explosions.
The researchers plan to further investigate this topic and utilize kilonovae explosions to gain insights into the detailed structure of neutron stars.