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Lecture 5

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PCS 181
Margaret Buckby

Class 9 Apparent size of Quasar = d = v t After we correct for the distance to the quasar, we find that QSO 3C273 was the size of a large star! How could the energy of 100 to 1000 galaxies be produced by an object the size of a large star ? How could this energy be produced from such a small volume? V r C*delta lamda/ Lamda lab V = H o D = V/H o The mechanism of a Quasar - Quasars are usually found in groups of galaxies. - The quasars and the galaxies have similar redshifts o Similar velocities o Similar distances o An association - “Fuzz” around Quasars shows stellar absorption spectra - Quasars are very luminous centers of distant, young galaxies. - Quasar energy is radiated by matter swirling in an accretion disk around a supermassive Black Hole. Summary of Quasar Properties - Small, compact, blue objects (x-rays are the dominant wavelength) - Looks like faint stars in photographs - X-ray emission - Large redshifts such that UV spectral lines appear in visible portion of the spectrum - Spectra are dominated by emission lines Know the names of the three spectra and how they are generated for the test (refer to the handout) - ~10% are radio sources - Optical luminosities are 100 to 1000 times that of normal galaxies - Many vary in intensity over days or weeks - Some quasars exhibit jets (optical or radio) Test 30 multiple choice questions 5 of them require use calculators Review from Bergmann’s lecture notes Photon: burst of energy Class 10 Material for Test 2 Unit 4: Birth of Stars…Lives of Stars Interstellar matter - This is dust and gas that occupy space between the stars - Stars form in the dust/gas clouds in space Dust - Dust is ~1% of the total visible mass in space - Obscures our view of distant objects - Is a mixture of o Elongated, tiny grains of dirty ice o Grains of graphite (carbon) o Silicate particles o Complex molecules Interstellar Reddening - Light from a star passes through the dust - The dust particles are ~same length as blue wavelength’s - The dust scatters blue wavelengths more than red wavelengths - More red photons pass unhindered through the dust and reach the observer. - Star appears redder than it actually is Gas There exists ~100 times more gas mass than dust mass in the universe Gas ~100 Dust The visi
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