Neutron Stars as Probes for the Structure of Dense Nuclear Matter

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Neutron Stars as Probes for the Structure of Dense Nuclear MatterFridolin Weber, San Diego State University, San Diego, CaliforniaNeutron stars contain matter in one of the densest forms found in theUniverse (a thimble full of such matter would have a mass of onebillion tons) which, together with the unprecedented progress inobservational astronomy, makes such stars superb astrophysicallaboratories for a broad range of fascinating physical studies. Theseinclude the exploration of nuclear processes in an environmentextremely rich of electrons and neutrons, and the formation of newstates of matter in the cores of such objects, like a plasma of quarksand gluons which is being sought at the most powerful terrestrialparticle colliders. This NSF supported research project aims atexploring such processes from observed neutron star data. It isdivided into two major activities.The first activity deals with X-ray neutron stars accreting matterfrom companions. Such neutron stars accrete typically many millionsof tons of matter per second, which hit the stellar surface at asignificant fraction of the speed of light. This leads tothermonuclear reactions on the stellar surface whose ashes gravitategradually inward, causing significant changes (e.g. nuclear fusionreactions) in the star's crust. The major goal of this activity is toexplore the impact of these thermonuclear reactions on the thermalevolution of accreting neutron stars.The second activity concerns our understanding of the fundamentalphysics realized in the ultra-dense core of neutron stars, whereneutrons and protons might be broken up into their quark constituents,creating a new state of matter known as quark matter. If quark matterexists in the cores of neutron stars, it will be a colorsuperconductor whose condensation pattern is very complex. It has alsobeen theorized that neutron stars could in fact be quark stars,objects made entirely of quark matter. In the framework of thisactivity, research on potential astrophysical signatures signaling theexistence of quark matter in "neutron" stars will be carried out.These research activities are crucial to obtain the full physicspotential of the investments that are made in astrophysical detectors,at Jefferson Lab, the Relativistic Heavy Ion Collider (RHIC), as wellas new investments that are recommended for the Rare IsotopeAccelerator (RIA).The researchers and students involved in this project will developmulti-media lectures on how stars work and present them to middleand high school students and teachers in the San Diego area.