Measuring cosmological parameters with gravitational waves from neutron star binaries

Abstract

Neutron stars are mysterious objects. Even though they are not very rare -about one in a thousand stars are thought to be neutron stars - we know very little about their physics. They are the densest known material objects in our universe, making Newtonian mechanics incapable of making any adequate predictions. Gravity is so strong in these stars, that it breaks atomic structure, compressing matter to several times the density of nuclei. As one can imagine, reproducing these conditions is impossible to do here on earth, which makes them hard to study. Their internal structure, described by the equation of state, is therefore unknown to us. Gravitational waves (GW) might just pro-vide a solution. Gravitational radiation is influenced by the properties of its source. Studying GW coming from neutron stars can provide us with knowledge about the extreme matter neutron stars consist of. This information can be extrapolated to cosmological parameters, such as the Hubble constant.