X射线天文观测.pdf

XX射线天文观测射线天文观测 王俊贤 中国科技大学天体物理中心 5/21/2012 • IInttrodductition • Detectors • A brief history of X-ray astronomy • XX-rayray targetstargets • Imaging technique • XX-ray obbservattoriies • Future • Cosmic X-ray Background (CXB) 5/21/2012 • High energy emission comes from regions withwith extremeextreme highhigh temperaturetemperature oror relativisticrelativistic velocity 5/21/2012 • PhPhotton energy unitit – kkeVV • Convert photon energy to wavelength 1 keV = 1.6 x 10-9 erg = hc/λ, λ=12.4Å the ionization potential of hydrogen: 13.6 eV or 912Å • Temperature 7 1 keV ~ 1.16 x 10 K ((hν= kT)) • Doppler shift a UV photon at 1240Å to 1keV require a speed of 0.9998c 5/21/2012 1895 Conrad Röntgen • ThThe fifirst PhPhysiics NNobbell PPriize WiWinner (1901)(1901) 5/21/2012 5/21/2012 Rapid growth of XRapid growth of X-ray astronomyray astronomy • SimpleSimple detectorsdetectors onon rocketrocket flight in 1962, equivalent to a naked eye in visible astronomy • A billion times more sensitive today, comparable to 10 meter optical telescopes 5/21/2012 • X-ray的光电吸收 • Compton scattering 电子经典散射截面 6.65x10-25 cm2 5/21/2012 Dust extinction versus XX-ray absorption Nray absorption NH GalacticGalactic ISMISM • absorptionabsorption lineline • absorptionabsorption edgeedge 5/21/2012 5/21/2012 X-ray scattering by dust –X-ray halohalo • Draine 2003 • 空气分子数密度空气分子数密度22.45x1045x1019 cmcm-3 • 空气中氧氮元素丰度空气中氧氮元素丰度~100100％％ • 太阳中金属元素丰度~0.2 ％ • 10 cm空气中对应太阳金属丰度大气柱密度 ~~ 22.5x105x102323 cmcm-22 5/21/2012 • ninety percent of the photons in a beam of 33 keVkeV XX-raysrays areare absorbedabsorbed byby travelingtraveling