In neutron stars, protons may do the heavy lifting

The positively charged particles may have an outsize influence on the properties of neutron stars and other neutron-rich objects.

Jennifer Chu | MIT News Office
August 13, 2018

Neutron stars are the smallest, densest stars in the universe, born out of the gravitational collapse of extremely massive stars. True to their name, neutron stars are composed almost entirely of neutrons — neutral subatomic particles that have been compressed into a small, incredibly dense celestial package.

A new study in Nature, co-led by MIT researchers including Or Hen, assistant professor of physics at MIT, suggests that some properties of neutron stars may be influenced not only by their multitude of densely packed neutrons, but also by a substantially smaller fraction of protons — positively charged particles that make up just 5 percent of a neutron star.

Instead of gazing at the stars, the researchers came to their conclusion by analyzing the microscopic nuclei of atoms on Earth.

The nucleus of an atom is packed with protons and neutrons, though not quite as densely as in neutron stars. Occasionally, if they are close enough in distance, a proton and a neutron will pair up and streak through an atom’s nucleus with unusually high energy. Such “short-range correlations,” as they are known, can contribute significantly to the energy balance and overall properties of a given atomic nucleus.  [Full article]