Neutron stars: probing physics at the extreme

点击翻译按钮获取中文摘要

A general theme threads my research: how is our understanding of astrophysical phenomena and fundamental physics connected. Neutron stars provide a laboratory to test our knowledge of nature at the extreme. The magnetic fields, densities and pressures of neutron stars exceed those produced on Earth more than a billion-fold. Neutron stars provide a unique opportunity to extrapolate and verify our theories of matter, energy and their interaction. My recent and future research program focusses on the theoretical and observational understanding of these and related objects. Neutron stars are the densest objects that we can directly observe in the universe --- the central singularity of a black hole is denser but it is hidden behind an event horizon and unobservable. At the end of a massive star's life, its core comprising of about one to two solar masses collapses to a sphere about ten kilometers in radius, the neutron star with a mean density of 1e15 g/cc, greater than the density of atomic nuclei. During the collapse the magnetic field of the core intensifies reaching 1e12 G typically and up to 1e15 G about ten percent of the time (forming a magnetar - this fraction is a recent result from my group). The phase of matter within the extremely dense cores of these objects lies beyond our current knowledge, and probing it is one goal of studying neutron stars. Above the core lies a crust (about 1 km thick) of material at subnuclear density. The phase of this material is known, but many of its properties have not yet been determined. This lower density material regulates the transfer of energy from the core to the surface, generating much of the phenomenology of neutron stars.