Astroparticle Physics

16 Glossary 305Stars which have rapid and unpredictable changes in brightness,mostly associated with a binary star system.See cosmic background radiation.Charge-Coupled Device, a solid-state camera.Strong galactic radio source in the constellation Centaurus.Type of pulsating variable stars where the period of oscillationis proportional to the average absolute magnitude; often used as‘standard’ candles.Centre Européen pour la Recherche Nucléaire. The major Europeancenter for particle physics located near Geneva in Switzerland.Compton Gamma-Ray Observatory. Satellite with four experimentson board for the measurement of galactic and extragalactic gammarays.X-ray satellite of the NASA (original name: AXAF) started in July1999; named after Subrahmanyan Chandrasekhar.Limiting mass for white dwarves (1.4 solar masses). If a star exceedsthis mass, gravity will eventually defeat the pressure of thedegenerate electron gas leading to a compact neutron star.Quantum number carried by a particle. The charge quantum numberdetermines whether a particle can participate in a special interactionprocess. Particles with electric charge participate in electromagneticinteractions, such with strong charge undergo stronginteractions, and those with weak charge are subject to weak interactions.The principle of charge invariance claims that all processes againconstitute a physical reality if particles are exchanged by their antiparticles.This principle is violated in weak interactions.The observation that the charge of a system of particles remains unchangedin an interaction or transformation. In this context chargestands for electric charge, strong charge, or also weak charge.Interaction process mediated by the exchange of a virtual chargedgauge boson.cataclysmic variablesCBRCCDCentaurus ACepheid variablesCERNCGROChandraChandrasekhar masschargecharge conjugationcharge conservationcharged currentc; the fourth quark flavour (if quarks are ordered with increasing charm quarkmass). The c quark has the electric charge + 2 3 e.For a given component in a particle mixture the chemical potentialdescribes the change in free energy with respect to a change in theamount of the component at fixed pressure and temperature.chemical potential