Fridolin Weber, San Diego State University, San Diego, California
Neutron stars contain matter in one of the densest forms found in the Universe (a thimble full of such matter would have a mass of one billion tons) which, together with the unprecedented progress in observational astronomy, makes such stars superb astrophysical laboratories for a broad range of fascinating physical studies. These include the exploration of nuclear processes in an environment extremely rich of electrons and neutrons, and the formation of new states of matter in the cores of such objects, like a plasma of quarks and gluons which is being sought at the most powerful terrestrial particle colliders. This NSF supported research project aims at exploring such processes from observed neutron star data. It is divided into two major activities.
The first activity deals with X-ray neutron stars accreting matter from companions. Such neutron stars accrete typically many millions of tons of matter per second, which hit the stellar surface at a significant fraction of the speed of light. This leads to thermonuclear reactions on the stellar surface whose ashes gravitate gradually inward, causing significant changes (e.g. nuclear fusion reactions) in the star's crust. The major goal of this activity is to explore the impact of these thermonuclear reactions on the thermal evolution of accreting neutron stars.
The second activity concerns our understanding of the fundamental physics realized in the ultra-dense core of neutron stars, where neutrons and protons might be broken up into their quark constituents, creating a new state of matter known as quark matter. If quark matter exists in the cores of neutron stars, it will be a color superconductor whose condensation pattern is very complex. It has also been theorized that neutron stars could in fact be quark stars, objects made entirely of quark matter. In the framework of this activity, research on potential astrophysical signatures signaling the existence of quark matter in "neutron" stars will be carried out.
These research activities are crucial to obtain the full physics potential of the investments that are made in astrophysical detectors, at Jefferson Lab, the Relativistic Heavy Ion Collider (RHIC), as well as new investments that are recommended for the Rare Isotope Accelerator (RIA).
The researchers and students involved in this project will develop multi-media lectures on how stars work and present them to middle and high school students and teachers in the San Diego area.
