Hybrid Stars

Abstract

Quark matter—which no doubt occupied the universe sometime in the first few seconds—may exist naturally today in the cores of neutron stars. The possibility was considered many years ago in the pioneering research of several authors (Itoh [296], Baym and Chin [297], Chapline and Nauenberg [298], and Keister and Kisslinger [299]). The earliest estimates suggested that hadronic matter would not convert to quark matter unless densities of the order 10ρ₀ were achieved [297]. Such densities are only marginally attainable in stellar models, so for some years the existence of quark matter in neutron stars seemed doubtful.