Massachusetts Institute of Technology | 2018 Aug 13
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, 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.
The researchers looked for signs of proton and neutron pairs in atoms of carbon, aluminum, iron, and lead, each with a progressively higher ratio of neutrons to protons. They found that, as the relative number of neutrons in an atom increased, so did the probability that a proton would form an energetic pair. The likelihood that a neutron would pair up, however, stayed about the same. This trend suggests that, in objects with high densities of neutrons, the minority protons carry a disproportionally large part of the average energy. ...
In Neutron Stars, Protons May Do the Heavy Lifting
American Friends of Tel Aviv University | 2018 Aug 14
Probing High-Momentum Protons and Neutrons in Neutron-Rich Nuclei - CLAS Collaboration
- Nature (online 13 Aug 2018) DOI: 10.1038/s41586-018-0400-z