Astroparticle Physics

320 16 GlossaryTotal light emission of a star or a galaxy in all ranges of wave-lengths. The luminosity therefore corresponds to the absolutebrightness.luminosityluminosity distanceMA measure of the relative brightness of a star or some other ce-lestial object. The brightness differences between two stars withintensities I 1 and I 2 are fixed through the magnitude m 1 − m 2 =−2.5log 10 (I 1 /I 2 ). The zero of this scale is defined in such a waythat the apparent brightness of the polestar comes out to be 2 m , 12.An apparent brightness difference of m = 2.5 corresponds to anintensity ratio of 10 : 1. On this scale the planet Venus has the magnitudem =−4.4. With the naked eye one can see stars down tothe magnitude m = 6. The strongest telescopes are able to observestars down to the 28th magnitude.M87MACHOMagellanic Cloudmagic numbersmagnetarmagnetic monopolemagnitudemain-sequence starThe distance to an astronomical object derived by comparing itsapparent brightness to its total known or presumed luminosity byassuming isotropic emission. If the luminosity is known, the sourcecan be used as standard candle.Galaxy in the Virgo cluster at a distance of 11 Mpc. M87 is consideredan excellent candidate for a source of high-energy cosmicrays.Massive Compact Halo Object. Experiment for the search for darkcompact objects in the halo of our Milky Way, see also EROS.Nearest galaxy neighbour to our Milky Way consisting of the Small(SMC) and the Large Magellanic Cloud (LMC); distance 52 kpc.Nuclei whose atomic number Z or neutron number N is one ofthe magic numbers 2, 8, 20, 28, 50, or 126. In the framework ofthe shell model of the nucleus these magic nucleon numbers formclosed shells. Nuclei whose proton and also neutron number aremagic are named doubly magic.Special class of neutron stars having a superstrong magnetic field(upto10 11 Tesla). Magnetars emit sporadic γ -ray bursts.Hypothetical particle which constitutes separate sources andcharges of the magnetic field. Magnetic monopoles are predictedby Grand Unified Theories.Star of average age lying on the main sequence in the Hertzsprung–Russell diagram.