Order-of-magnitude physics of neutron stars

TL;DR

This paper provides an accessible, physics-based overview of neutron star properties, including their maximum mass, rotation, and electromagnetic features, suitable for advanced undergraduates.

Contribution

It introduces a simplified, educational approach to estimating neutron star characteristics using basic physics and scaling relations.

Findings

Estimated neutron star maximum mass using simple physics.

Discussed the rotational and electromagnetic properties of neutron stars.

Connected properties of matter on Earth to neutron star physics.

Abstract

We use basic physics and simple mathematics accessible to advanced undergraduate students to estimate the main properties of neutron stars. We set the stage and introduce relevant concepts by discussing the properties of "everyday" matter on Earth, degenerate Fermi gases, white dwarfs, and scaling relations of stellar properties with polytropic equations of state. Then, we discuss various physical ingredients relevant for neutron stars and how they can be combined in order to obtain a couple of different simple estimates of their maximum mass, beyond which they would collapse, turning into black holes. Finally, we use the basic structural parameters of neutron stars to briefly discuss their rotational and electromagnetic properties.