Eur. Phys. J. A (2016) 52: 52
https://doi.org/10.1140/epja/i2016-16052-y

Review

Order-of-magnitude physics of neutron stars

Estimating their properties from first principles

Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436, Macul, Chile

^* e-mail: areisene@astro.puc.cl

Received: 20 August 2015
Revised: 16 November 2015
Accepted: 24 November 2015
Published online: 16 March 2016

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.